diff --git a/src/Helpers/StringableValue.php b/src/Helpers/StringableValue.php
new file mode 100644
index 0000000..cfae9e1
--- /dev/null
+++ b/src/Helpers/StringableValue.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace ByJoby\HTML\Helpers;
+
+use Stringable;
+
+/**
+ * Class for automatically serializing and unserializing text values (such as in
+ * attributes) between a text representation that can be rendered and an object
+ * representation that is easy to work with.
+ *
+ * Objects that implement this can be passed into an Attributes object and will
+ * be stored as their object form and automatically converted into strings at
+ * render time. Some tags will have specific requirements for particular
+ * implementations of this interface for particular attribute getters/setters.
+ */
+interface StringableValue extends Stringable
+{
+    public static function fromString(string|Stringable|null $string): self|null;
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/BTag.php b/src/Html5/InlineTextSemantics/BTag.php
new file mode 100644
index 0000000..5f2af7c
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/BTag.php
@@ -0,0 +1,34 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <b> HTML element is used to draw the reader's attention to the element's
+ * contents, which are not otherwise granted special importance. This was
+ * formerly known as the Boldface element, and most browsers still draw the text
+ * in boldface. However, you should not use <b> for styling text or granting
+ * importance. If you wish to create boldface text, you should use the CSS
+ * font-weight property. If you wish to indicate an element is of special
+ * importance, you should use the <strong> element.
+ *
+ * Do not confuse the <b> element with the <strong>, <em>, or <mark> elements.
+ * The <strong> element represents text of certain importance, <em> puts some
+ * emphasis on the text and the <mark> element represents text of certain
+ * relevance. The <b> element doesn't convey such special semantic information;
+ * use it only when no others fit.
+ *
+ * It is a good practice to use the class attribute on the <b> element in order
+ * to convey additional semantic information as needed (for example <b
+ * class="lead"> for the first sentence in a paragraph). This makes it easier to
+ * manage multiple use cases of <b> if your stylistic needs change, without the
+ * need to change all of its uses in the HTML.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/b
+ */
+class BTag extends AbstractContainerTag
+{
+    const TAG = 'b';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/BdiTag.php b/src/Html5/InlineTextSemantics/BdiTag.php
new file mode 100644
index 0000000..f5e13a7
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/BdiTag.php
@@ -0,0 +1,29 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <bdi> HTML element tells the browser's bidirectional algorithm to treat
+ * the text it contains in isolation from its surrounding text. It's
+ * particularly useful when a website dynamically inserts some text and doesn't
+ * know the directionality of the text being inserted.
+ *
+ * Bidirectional text is text that may contain both sequences of characters that
+ * are arranged left-to-right (LTR) and sequences of characters that are
+ * arranged right-to-left (RTL), such as an Arabic quotation embedded in an
+ * English string. Browsers implement the Unicode Bidirectional Algorithm to
+ * handle this. In this algorithm, characters are given an implicit
+ * directionality: for example, Latin characters are treated as LTR while Arabic
+ * characters are treated as RTL. Some other characters (such as spaces and some
+ * punctuation) are treated as neutral and are assigned directionality based on
+ * that of their surrounding characters.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/bdi
+ */
+class BdiTag extends AbstractContainerTag
+{
+    const TAG = 'bdi';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/BdoTag.php b/src/Html5/InlineTextSemantics/BdoTag.php
new file mode 100644
index 0000000..fde7679
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/BdoTag.php
@@ -0,0 +1,17 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <bdo> HTML element overrides the current directionality of text, so that
+ * the text within is rendered in a different direction.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/bdo
+ */
+class BdoTag extends AbstractContainerTag
+{
+    const TAG = 'bdo';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/BrTag.php b/src/Html5/InlineTextSemantics/BrTag.php
new file mode 100644
index 0000000..8dfd5c2
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/BrTag.php
@@ -0,0 +1,16 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractTag;
+
+/**
+ * The <br> HTML element produces a line break in text (carriage-return). It is useful for writing a poem or an address, where the division of lines is significant.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/br
+ */
+class BrTag extends AbstractTag
+{
+    const TAG = 'br';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/CiteTag.php b/src/Html5/InlineTextSemantics/CiteTag.php
new file mode 100644
index 0000000..814809e
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/CiteTag.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <cite> HTML element is used to mark up the title of a cited creative
+ * work. The reference may be in an abbreviated form according to
+ * context-appropriate conventions related to citation metadata.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/cite
+ */
+class CiteTag extends AbstractContainerTag
+{
+    const TAG = 'cite';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/CodeTag.php b/src/Html5/InlineTextSemantics/CodeTag.php
new file mode 100644
index 0000000..b0ed844
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/CodeTag.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <code> HTML element displays its contents styled in a fashion intended to
+ * indicate that the text is a short fragment of computer code. By default, the
+ * content text is displayed using the user agent's default monospace font.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/code
+ */
+class CodeTag extends AbstractContainerTag
+{
+    const TAG = 'code';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/DataTag.php b/src/Html5/InlineTextSemantics/DataTag.php
new file mode 100644
index 0000000..e025132
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/DataTag.php
@@ -0,0 +1,56 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+use Stringable;
+
+/**
+ * The <data> HTML element links a given piece of content with a
+ * machine-readable translation. If the content is time- or date-related, the
+ * <time> element must be used.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/data
+ */
+class DataTag extends AbstractContainerTag
+{
+    const TAG = 'data';
+
+    /**
+     * This attribute specifies the machine-readable translation of the content
+     * of the element.
+     *
+     * @return null|string|Stringable
+     */
+    public function value(): null|string|Stringable
+    {
+        return $this->attributes()->asString('value');
+    }
+
+    /**
+     * This attribute specifies the machine-readable translation of the content
+     * of the element.
+     *
+     * @param null|string|Stringable $value
+     * @return static
+     */
+    public function setValue(null|string|Stringable $value): static
+    {
+        if ($value) $this->attributes()['value'] = $value;
+        else $this->unsetValue();
+        return $this;
+    }
+
+    /**
+     * This attribute specifies the machine-readable translation of the content
+     * of the element.
+     *
+     * @return static
+     */
+    public function unsetValue(): static
+    {
+        unset($this->attributes()['value']);
+        return $this;
+    }
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/DfnTag.php b/src/Html5/InlineTextSemantics/DfnTag.php
new file mode 100644
index 0000000..a42a3b9
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/DfnTag.php
@@ -0,0 +1,76 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+use Stringable;
+
+/**
+ * The <dfn> HTML element is used to indicate the term being defined within the
+ * context of a definition phrase or sentence. The ancestor <p> element, the
+ * <dt>/<dd> pairing, or the nearest <section> ancestor of the <dfn> element, is
+ * considered to be the definition of the term.
+ *
+ * The term being defined is identified following these rules:
+ *
+ *  * If the <dfn> element has a title attribute, the value of the title
+ *    attribute is considered to be the term being defined. The element must
+ *    still have text within it, but that text may be an abbreviation (perhaps
+ *    using <abbr>) or another form of the term.
+ *  * If the <dfn> contains a single child element and does not have any text
+ *    content of its own, and the child element is an <abbr> element with a
+ *    title attribute itself, then the exact value of the <abbr> element's title
+ *    is the term being defined.
+ *  * Otherwise, the text content of the <dfn> element is the term being
+ *    defined. This is shown in the first example below.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/dfn
+ */
+class DataTag extends AbstractContainerTag
+{
+    const TAG = 'dfn';
+
+    /**
+     * If the <dfn> element has a title attribute, the value of the title
+     * attribute is considered to be the term being defined. The element must
+     * still have text within it, but that text may be an abbreviation (perhaps
+     * using <abbr>) or another form of the term.
+     *
+     * @return null|string|Stringable
+     */
+    public function title(): null|string|Stringable
+    {
+        return $this->attributes()->asString('title');
+    }
+
+    /**
+     * If the <dfn> element has a title attribute, the value of the title
+     * attribute is considered to be the term being defined. The element must
+     * still have text within it, but that text may be an abbreviation (perhaps
+     * using <abbr>) or another form of the term.
+     *
+     * @param null|string|Stringable $title
+     * @return static
+     */
+    public function setTitle(null|string|Stringable $title): static
+    {
+        if ($title) $this->attributes()['title'] = $title;
+        else $this->unsetTitle();
+        return $this;
+    }
+
+    /**
+     * If the <dfn> element has a title attribute, the value of the title
+     * attribute is considered to be the term being defined. The element must
+     * still have text within it, but that text may be an abbreviation (perhaps
+     * using <abbr>) or another form of the term.
+     *
+     * @return static
+     */
+    public function unsetTitle(): static
+    {
+        unset($this->attributes()['title']);
+        return $this;
+    }
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/EmTag.php b/src/Html5/InlineTextSemantics/EmTag.php
new file mode 100644
index 0000000..18a0c82
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/EmTag.php
@@ -0,0 +1,30 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <em> HTML element marks text that has stress emphasis. The <em> element
+ * can be nested, with each level of nesting indicating a greater degree of
+ * emphasis.
+ *
+ * The <em> element is for words that have a stressed emphasis compared to
+ * surrounding text, which is often limited to a word or words of a sentence and
+ * affects the meaning of the sentence itself.
+ *
+ * Typically this element is displayed in italic type. However, it should not be
+ * used to apply italic styling; use the CSS font-style property for that
+ * purpose. Use the <cite> element to mark the title of a work (book, play,
+ * song, etc.). Use the <i> element to mark text that is in an alternate tone or
+ * mood, which covers many common situations for italics such as scientific
+ * names or words in other languages. Use the <strong> element to mark text that
+ * has greater importance than surrounding text.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/em
+ */
+class EmTag extends AbstractContainerTag
+{
+    const TAG = 'em';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/ITag.php b/src/Html5/InlineTextSemantics/ITag.php
new file mode 100644
index 0000000..08bda76
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/ITag.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <i> HTML element represents a range of text that is set off from the
+ * normal text for some reason, such as idiomatic text, technical terms,
+ * taxonomical designations, among others. Historically, these have been
+ * presented using italicized type, which is the original source of the <i>
+ * naming of this element.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/i
+ */
+class ITag extends AbstractContainerTag
+{
+    const TAG = 'i';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/KbdTag.php b/src/Html5/InlineTextSemantics/KbdTag.php
new file mode 100644
index 0000000..dfef24a
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/KbdTag.php
@@ -0,0 +1,27 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <kbd> HTML element represents a span of inline text denoting textual user
+ * input from a keyboard, voice input, or any other text entry device. By
+ * convention, the user agent defaults to rendering the contents of a <kbd>
+ * element using its default monospace font, although this is not mandated by
+ * the HTML standard.
+ *
+ * To describe an input comprised of multiple keystrokes, you can nest multiple
+ * <kbd> elements, with an outer <kbd> element representing the overall input
+ * and each individual keystroke or component of the input enclosed within its
+ * own <kbd>, such as:
+ *
+ * <kbd><kbd>Ctrl</kbd>+<kbd>N</kbd></kbd>
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/kbd
+ */
+class KbdTag extends AbstractContainerTag
+{
+    const TAG = 'kbd';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/MarkTag.php b/src/Html5/InlineTextSemantics/MarkTag.php
new file mode 100644
index 0000000..b8d5dc7
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/MarkTag.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <mark> HTML element represents text which is marked or highlighted for
+ * reference or notation purposes due to the marked passage's relevance in the
+ * enclosing context.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/mark
+ */
+class MarkTag extends AbstractContainerTag
+{
+    const TAG = 'mark';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/QTag.php b/src/Html5/InlineTextSemantics/QTag.php
new file mode 100644
index 0000000..69116f7
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/QTag.php
@@ -0,0 +1,60 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+use Stringable;
+
+/**
+ * The <q> HTML element indicates that the enclosed text is a short inline
+ * quotation. Most modern browsers implement this by surrounding the text in
+ * quotation marks. This element is intended for short quotations that don't
+ * require paragraph breaks; for long quotations use the <blockquote> element.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/q
+ */
+class QTag extends AbstractContainerTag
+{
+    const TAG = 'q';
+
+    /**
+     * The value of this attribute is a URL that designates a source document or
+     * message for the information quoted. This attribute is intended to point
+     * to information explaining the context or the reference for the quote.
+     *
+     * @return null|string|Stringable
+     */
+    public function cite(): null|string|Stringable
+    {
+        return $this->attributes()->asString('cite');
+    }
+
+    /**
+     * The value of this attribute is a URL that designates a source document or
+     * message for the information quoted. This attribute is intended to point
+     * to information explaining the context or the reference for the quote.
+     *
+     * @param null|string|Stringable $cite
+     * @return static
+     */
+    public function setCite(null|string|Stringable $cite): static
+    {
+        if ($cite) $this->attributes()['cite'] = $cite;
+        else $this->unsetCite();
+        return $this;
+    }
+
+    /**
+     * The value of this attribute is a URL that designates a source document or
+     * message for the information quoted. This attribute is intended to point
+     * to information explaining the context or the reference for the quote.
+     *
+     * @return static
+     */
+    public function unsetCite(): static
+    {
+        unset($this->attributes()['cite']);
+        return $this;
+    }
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/RpTag.php b/src/Html5/InlineTextSemantics/RpTag.php
new file mode 100644
index 0000000..0795827
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/RpTag.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <rp> HTML element is used to provide fall-back parentheses for browsers
+ * that do not support display of ruby annotations using the <ruby> element. One
+ * <rp> element should enclose each of the opening and closing parentheses that
+ * wrap the <rt> element that contains the annotation's text.
+ *
+ * Ruby annotations are for showing pronunciation of East Asian characters, like
+ * using Japanese furigana or Taiwanese bopomofo characters. The <rp> element is
+ * used in the case of lack of <ruby> element support; the <rp> content provides
+ * what should be displayed in order to indicate the presence of a ruby
+ * annotation, usually parentheses.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/rp
+ */
+class RpTag extends AbstractContainerTag
+{
+    const TAG = 'rp';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/RtTag.php b/src/Html5/InlineTextSemantics/RtTag.php
new file mode 100644
index 0000000..1d00188
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/RtTag.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <rt> HTML element specifies the ruby text component of a ruby annotation,
+ * which is used to provide pronunciation, translation, or transliteration
+ * information for East Asian typography. The <rt> element must always be
+ * contained within a <ruby> element.
+ *
+ * This simple example provides Romaji transliteration for the kanji characters
+ * within the <ruby> element:
+ *
+ * <ruby> 漢 <rt>Kan</rt> 字 <rt>ji</rt> </ruby>
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/rt
+ */
+class RtTag extends AbstractContainerTag
+{
+    const TAG = 'rt';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/RubyTag.php b/src/Html5/InlineTextSemantics/RubyTag.php
new file mode 100644
index 0000000..8922f24
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/RubyTag.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <ruby> HTML element represents small annotations that are rendered above,
+ * below, or next to base text, usually used for showing the pronunciation of
+ * East Asian characters. It can also be used for annotating other kinds of
+ * text, but this usage is less common.
+ *
+ * Example 1: Character:
+ * ```
+ * <ruby>
+ *   漢 <rp>(</rp><rt>Kan</rt><rp>)</rp>
+ *   字 <rp>(</rp><rt>ji</rt><rp>)</rp>
+ * </ruby>
+ * ```
+ * 
+ * Example 2: Word
+ * ```
+ * <ruby> 明日 <rp>(</rp><rt>Ashita</rt><rp>)</rp> </ruby>
+ * ```
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/ruby
+ */
+class RubyTag extends AbstractContainerTag
+{
+    const TAG = 'ruby';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/STag.php b/src/Html5/InlineTextSemantics/STag.php
new file mode 100644
index 0000000..872260a
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/STag.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <s> HTML element renders text with a strikethrough, or a line through it.
+ * Use the <s> element to represent things that are no longer relevant or no
+ * longer accurate. However, <s> is not appropriate when indicating document
+ * edits; for that, use the <del> and <ins> elements, as appropriate.
+ *
+ * Accessibility concerns: The presence of the s element is not announced by
+ * most screen reading technology in its default configuration. It can be made
+ * to be announced by using the CSS content property, along with the ::before
+ * and ::after pseudo-elements.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/s
+ */
+class STag extends AbstractContainerTag
+{
+    const TAG = 's';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/SampTag.php b/src/Html5/InlineTextSemantics/SampTag.php
new file mode 100644
index 0000000..506f896
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/SampTag.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <samp> HTML element is used to enclose inline text which represents
+ * sample (or quoted) output from a computer program. Its contents are typically
+ * rendered using the browser's default monospaced font (such as Courier or
+ * Lucida Console).
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/samp
+ */
+class SampTag extends AbstractContainerTag
+{
+    const TAG = 'samp';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/SmallTag.php b/src/Html5/InlineTextSemantics/SmallTag.php
new file mode 100644
index 0000000..c751840
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/SmallTag.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <small> HTML element represents side-comments and small print, like
+ * copyright and legal text, independent of its styled presentation. By default,
+ * it renders text within it one font-size smaller, such as from small to
+ * x-small.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/small
+ */
+class SmallTag extends AbstractContainerTag
+{
+    const TAG = 'small';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/SpanTag.php b/src/Html5/InlineTextSemantics/SpanTag.php
new file mode 100644
index 0000000..4951617
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/SpanTag.php
@@ -0,0 +1,22 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <span> HTML element is a generic inline container for phrasing content,
+ * which does not inherently represent anything. It can be used to group
+ * elements for styling purposes (using the class or id attributes), or because
+ * they share attribute values, such as lang. It should be used only when no
+ * other semantic element is appropriate. <span> is very much like a <div>
+ * element, but <div> is a block-level element whereas a <span> is an
+ * inline-level element.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/span
+ */
+class SpanTag extends AbstractContainerTag
+{
+    const TAG = 'span';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/StrongTag.php b/src/Html5/InlineTextSemantics/StrongTag.php
new file mode 100644
index 0000000..dfb039d
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/StrongTag.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <strong> HTML element indicates that its contents have strong importance,
+ * seriousness, or urgency. Browsers typically render the contents in bold type.
+ *
+ * The <strong> element is for content that is of "strong importance," including
+ * things of great seriousness or urgency (such as warnings). This could be a
+ * sentence that is of great importance to the whole page, or you could merely
+ * try to point out that some words are of greater importance compared to nearby
+ * content.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/strong
+ */
+class StrongTag extends AbstractContainerTag
+{
+    const TAG = 'strong';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/SubTag.php b/src/Html5/InlineTextSemantics/SubTag.php
new file mode 100644
index 0000000..3ba99df
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/SubTag.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <sub> HTML element specifies inline text which should be displayed as
+ * subscript for solely typographical reasons. Subscripts are typically rendered
+ * with a lowered baseline using smaller text.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/sub
+ */
+class SubTag extends AbstractContainerTag
+{
+    const TAG = 'sub';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/SupTag.php b/src/Html5/InlineTextSemantics/SupTag.php
new file mode 100644
index 0000000..e736dfb
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/SupTag.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Tags\AbstractContainerTag;
+
+/**
+ * The <sup> HTML element specifies inline text which is to be displayed as
+ * superscript for solely typographical reasons. Superscripts are usually
+ * rendered with a raised baseline using smaller text.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/sup
+ */
+class SupTag extends AbstractContainerTag
+{
+    const TAG = 'sup';
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/TimeTag.php b/src/Html5/InlineTextSemantics/TimeTag.php
new file mode 100644
index 0000000..f64ea29
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/TimeTag.php
@@ -0,0 +1,49 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics;
+
+use ByJoby\HTML\Html5\InlineTextSemantics\TimeTag\DatetimeValue;
+use ByJoby\HTML\Tags\AbstractContainerTag;
+use DateInterval;
+use DateTimeInterface;
+use Stringable;
+
+/**
+ * The <time> HTML element represents a specific period in time. It may include
+ * the datetime attribute to translate dates into machine-readable format,
+ * allowing for better search engine results or custom features such as
+ * reminders.
+ *
+ * It may represent one of the following:
+ *  * A time on a 24-hour clock.
+ *  * A precise date in the Gregorian calendar (with optional time and timezone
+ *    information).
+ *  * A valid time duration.
+ *
+ * Tag description by Mozilla Contributors licensed under CC-BY-SA 2.5
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/time
+ */
+class TimeTag extends AbstractContainerTag
+{
+    const TAG = 'time';
+
+    public function datetime(): null|DatetimeValue
+    {
+        return DatetimeValue::fromString(
+            $this->attributes()->asString('datetime')
+        );
+    }
+
+    public function setDatetime(null|DatetimeValue $datetime): static
+    {
+        if ($datetime) $this->attributes()['datetime'] = $datetime;
+        else $this->unsetDatetime();
+        return $this;
+    }
+
+    public function unsetDatetime(): static
+    {
+        unset($this->attributes()['datetime']);
+        return $this;
+    }
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue.php b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue.php
new file mode 100644
index 0000000..2761650
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue.php
@@ -0,0 +1,76 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use ByJoby\HTML\Helpers\StringableValue;
+use Stringable;
+
+abstract class DatetimeValue implements StringableValue
+{
+    /** @var array<int,class-string<DatetimeValue>> */
+    const SUBCLASSES = [
+        DatetimeValue_datetime::class,
+        DatetimeValue_datetime_local::class,
+        DatetimeValue_time::class,
+        DatetimeValue_year::class,
+        DatetimeValue_month::class,
+        DatetimeValue_date::class,
+        DatetimeValue_date_yearless::class,
+        DatetimeValue_week::class,
+        DatetimeValue_duration::class,
+    ];
+
+    /**
+     * Matches any sequence of at least four digits, optionally prefixed with a
+     * dash for negative (BCE) years
+     */
+    const REGEX_YEAR = '(?<year>(\-)?[0-9]{4,})';
+
+    /**
+     * Matches any integer from 01 to 12, leading zero optional
+     */
+    const REGEX_MONTH = '(?<month>0?[1-9]|1[0-2])';
+
+    /**
+     * Matches any integer from 01 to 31, leading zero optional
+     */
+    const REGEX_DAY = '(?<day>0?[1-9]|[0-2][0-9]|3[0-1])';
+
+    /**
+     * Matches any integer from 01 to 53, leading zero optional
+     */
+    const REGEX_WEEKNUM = '(?<weeknum>0?[1-9]|[1-4][0-9]|5[0-3])';
+
+    /**
+     * Matches any integer from 00 to 59, leading zero optional
+     */
+    const REGEX_HOUR = '(?<hour>0?[0-9]|1[0-9]|2[0-3])';
+
+    /**
+     * Matches any integer from 00 to 59, leading zero optional
+     */
+    const REGEX_MINUTE = '(?<minute>0?[0-9]|[1-5][0-9])';
+
+    /**
+     * Matches any integer from 00 to 59, leading zero optional. Optionally
+     * followed by a three-digit decimal portion.
+     */
+    const REGEX_SECOND = '((?<second>0?[0-9]|[1-5][0-9])(\.(?<microsecond>[0-9]{3}))?)';
+
+    /**
+     * Tries parsing with all subclasses and returns the first one that
+     * succeeds, or null if nothing does.
+     *
+     * @param string|Stringable|null $string
+     * @return null|self
+     */
+    public static function fromString(string|Stringable|null $string): null|self
+    {
+        if (is_null($string)) return null;
+        foreach (static::SUBCLASSES as $class) {
+            $result = $class::fromString(strval($string));
+            if ($result) return $result;
+        }
+        return null;
+    }
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date.php b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date.php
new file mode 100644
index 0000000..01a8d6a
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use DateTime;
+use Stringable;
+
+/**
+ * Holds a date that will be stringed to something like 2011-11-18
+ *
+ * Stored internally as a DateTime with the time set to noon, which is public
+ * and as such can be conveniently manipulated.
+ */
+class DatetimeValue_date extends DatetimeValue
+{
+    /** @var DateTime */
+    public $datetime;
+
+    public static function fromString(string|Stringable|null $string): null|self
+    {
+        // null string returns null
+        if (is_null($string)) return null;
+        // try to match regular expression
+        elseif (
+            preg_match(
+                sprintf(
+                    '/^%s\-%s\-%s$/',
+                    static::REGEX_YEAR,
+                    static::REGEX_MONTH,
+                    static::REGEX_DAY,
+                ),
+                $string,
+                $matches
+            )
+        ) {
+            return new self(
+                intval($matches['year']),
+                intval($matches['month']),
+                intval($matches['day']),
+            );
+        }
+        // return null if nothing found
+        return null;
+    }
+
+    public function __construct(int $year, int $month, int $day)
+    {
+        $this->datetime = (new DateTime())
+            ->setDate($year,$month,$day)
+            ->setTime(12,0,0,0);
+    }
+
+    public function __toString()
+    {
+        return $this->datetime->format('Y-m-d');
+    }
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_yearless.php b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_yearless.php
new file mode 100644
index 0000000..611b46f
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_yearless.php
@@ -0,0 +1,56 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use DateTime;
+use Stringable;
+
+/**
+ * Holds a date that will be stringed to something like 11-18
+ *
+ * Stored internally as a DateTime with the time set to noon, which is public
+ * and as such can be conveniently manipulated. Internally the year will be set
+ * to the current year.
+ */
+class DatetimeValue_date_yearless extends DatetimeValue
+{
+    /** @var DateTime */
+    public $datetime;
+
+    public static function fromString(string|Stringable|null $string): null|self
+    {
+        // null string returns null
+        if (is_null($string)) return null;
+        // try to match regular expression
+        elseif (
+            preg_match(
+                sprintf(
+                    '/^%s\-%s$/',
+                    static::REGEX_MONTH,
+                    static::REGEX_DAY,
+                ),
+                $string,
+                $matches
+            )
+        ) {
+            return new self(
+                intval($matches['month']),
+                intval($matches['day']),
+            );
+        }
+        // return null if nothing found
+        return null;
+    }
+
+    public function __construct(int $month, int $day)
+    {
+        $this->datetime = (new DateTime())
+            ->setDate(intval(date('Y')), $month, $day)
+            ->setTime(12, 0, 0, 0);
+    }
+
+    public function __toString()
+    {
+        return $this->datetime->format('m-d');
+    }
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_datetime.php b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_datetime.php
new file mode 100644
index 0000000..3f2df93
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_datetime.php
@@ -0,0 +1,84 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use DateTime;
+use DateTimeZone;
+use Stringable;
+
+/**
+ * Holds a date/time that will be stringed to something like
+ * 2011-11-18T14:54:39.929-0600
+ *
+ * Stored internally as a DateTime, which is public and as such can be
+ * conveniently manipulated.
+ */
+class DatetimeValue_datetime extends DatetimeValue
+{
+    /**
+     * Matches either "Z" or a positive or negative offset from GMT in which the
+     * colon is optional, such as +04:00 or -1030
+     */
+    const REGEX_TIMEZONE = '(?<timezone>Z|(\+|\-)(0[0-9]|1[0-9]|2[0-3]):?(0[0-9]|[0-5][0-9]))';
+
+    public static function fromString(string|Stringable|null $string): null|self
+    {
+        // null string returns null
+        if (is_null($string)) return null;
+        // try to match regular expression
+        elseif (
+            preg_match(
+                sprintf(
+                    '/^%s\-%s\-%s(T| )%s:%s(:%s)?%s$/i',
+                    static::REGEX_YEAR,
+                    static::REGEX_MONTH,
+                    static::REGEX_DAY,
+                    static::REGEX_HOUR,
+                    static::REGEX_MINUTE,
+                    static::REGEX_SECOND,
+                    static::REGEX_TIMEZONE,
+                ),
+                $string,
+                $matches
+            )
+        ) {
+            return new self(
+                (new DateTime())
+                    ->setTimezone(
+                        self::parseTimezone($matches['timezone'])
+                    )
+                    ->setDate(
+                        intval($matches['year']),
+                        intval($matches['month']),
+                        intval($matches['day'])
+                    )
+                    ->setTime(
+                        intval($matches['hour']),
+                        intval($matches['minute']),
+                        intval(@$matches['second']),
+                        intval(@$matches['millisecond']) * 1000
+                    )
+            );
+        }
+        // return null if nothing found
+        return null;
+    }
+
+    protected static function parseTimezone(string $timezone): DateTimeZone
+    {
+        if ($timezone == 'Z' || $timezone == 'z') {
+            return new DateTimeZone('UTC');
+        } else {
+            return new DateTimeZone(str_replace(':', '', $timezone));
+        }
+    }
+
+    public function __construct(public DateTime $datetime)
+    {
+    }
+
+    public function __toString()
+    {
+        return $this->datetime->format('c');
+    }
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_datetime_local.php b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_datetime_local.php
new file mode 100644
index 0000000..16d43ed
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_datetime_local.php
@@ -0,0 +1,65 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use DateTime;
+use Stringable;
+
+/**
+ * Holds a date/time that will be stringed to something like
+ * 2011-11-18T14:54:39.929 for use as a local time without an attached timezone.
+ *
+ * Stored internally as a DateTime, which is public and as such can be
+ * conveniently manipulated.
+ */
+class DatetimeValue_datetime_local extends DatetimeValue
+{
+    /** @var DateTime */
+    public $datetime;
+
+    public static function fromString(string|Stringable|null $string): null|self
+    {
+        // null string returns null
+        if (is_null($string)) return null;
+        // try to match regular expression
+        elseif (
+            preg_match(
+                sprintf(
+                    '/^%s\-%s\-%s(t|T| )%s:%s(:%s)?$/',
+                    static::REGEX_YEAR,
+                    static::REGEX_MONTH,
+                    static::REGEX_DAY,
+                    static::REGEX_HOUR,
+                    static::REGEX_MINUTE,
+                    static::REGEX_SECOND,
+                ),
+                $string,
+                $matches
+            )
+        ) {
+            return new self(
+                intval($matches['year']),
+                intval($matches['month']),
+                intval($matches['day']),
+                intval($matches['hour']),
+                intval($matches['minute']),
+                intval(@$matches['second']),
+                intval(@$matches['millisecond'])
+            );
+        }
+        // return null if nothing found
+        return null;
+    }
+
+    public function __construct(int $year, int $month, int $day, int $hour, int $minute, int $second = 0, int $millisecond = 0)
+    {
+        $this->datetime = (new DateTime())
+            ->setDate($year, $month, $day)
+            ->setTime($hour, $minute, $second, $millisecond * 1000);
+    }
+
+    public function __toString()
+    {
+        return $this->datetime->format('Y-m-d\TH:i:s.v');
+    }
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_duration.php b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_duration.php
new file mode 100644
index 0000000..1648896
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_duration.php
@@ -0,0 +1,48 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use DateInterval;
+use Stringable;
+
+/**
+ * Holds an interval/duration that will be stringed to something like PT4H18M3S
+ */
+class DatetimeValue_duration extends DatetimeValue
+{
+    /**
+     * Matches a valid duration period designation
+     */
+    const REGEX_DURATION = "(<duration>P([0-9]+Y)?([0-9]+M)?([0-9]+[WD])?(T([0-9]+H)?([0-9]+M)?([0-9]+S)?)?)";
+
+    public static function fromString(string|Stringable|null $string): null|self
+    {
+        // null string returns null
+        if (is_null($string)) return null;
+        // try to construct
+        try {
+            return new self(
+                new DateInterval(strval($string))
+            );
+        } catch (\Throwable $th) {
+            return null;
+        }
+    }
+
+    public function __construct(protected DateInterval $interval)
+    {
+    }
+
+    public function __toString()
+    {
+        // format with all fields
+        $string = $this->interval->format('P%yY%mM%dDT%hH%iM%sS');
+        // strip out fields that are zero
+        /** @var string */
+        $string = preg_replace('/0[YMDHMS]/', '', $string);
+        // strip trailing T if necessary
+        if (str_ends_with($string, 'T')) $string = substr($string, 0, strlen($string) - 1);
+        // return cleaned up value
+        return $string;
+    }
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_month.php b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_month.php
new file mode 100644
index 0000000..b3d47dd
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_month.php
@@ -0,0 +1,50 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use Stringable;
+
+/**
+ * Holds a year/month pair that will be stringed to something like 2011-11
+ */
+class DatetimeValue_month extends DatetimeValue
+{
+    public static function fromString(string|Stringable|null $string): null|self
+    {
+        // null string returns null
+        if (is_null($string)) return null;
+        // try to match regular expression
+        elseif (
+            preg_match(
+                sprintf(
+                    '/^%s\-%s$/',
+                    static::REGEX_YEAR,
+                    static::REGEX_MONTH
+                ),
+                $string,
+                $matches
+            )
+        ) {
+            return new self(
+                intval($matches['year']),
+                intval($matches['month'])
+            );
+        }
+        // return null if nothing found
+        return null;
+    }
+
+    public function __construct(public int $year, public int $week)
+    {
+    }
+
+    public function __toString()
+    {
+        return sprintf(
+            '%s%04d-%02d',
+            $this->year < 0 ? '-' : '',
+            abs($this->year),
+            $this->week
+        );
+    }
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_time.php b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_time.php
new file mode 100644
index 0000000..39c49b7
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_time.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use DateTime;
+use Stringable;
+
+/**
+ * Holds a time that will be stringed to something like 14.54:39.929
+ *
+ * Stored internally as a DateTime with the date set to today, which is public
+ * and as such can be conveniently manipulated.
+ */
+class DatetimeValue_time extends DatetimeValue
+{
+    /** @var DateTime */
+    public $datetime;
+
+    public static function fromString(string|Stringable|null $string): null|self
+    {
+        // null string returns null
+        if (is_null($string)) return null;
+        // try to match regular expression
+        elseif (
+            preg_match(
+                sprintf(
+                    '/^%s:%s(:%s)?$/',
+                    static::REGEX_HOUR,
+                    static::REGEX_MINUTE,
+                    static::REGEX_SECOND,
+                ),
+                $string,
+                $matches
+            )
+        ) {
+            return new self(
+                intval($matches['hour']),
+                intval($matches['minute']),
+                intval(@$matches['second']),
+                intval(@$matches['microsecond'])
+            );
+        }
+        // return null if nothing found
+        return null;
+    }
+
+    public function __construct(int $hour, int $minute, int $second = 0, int $millisecond = 0)
+    {
+        $this->datetime = (new DateTime())
+            ->setTime($hour, $minute, $second, $millisecond*1000);
+    }
+
+    public function __toString()
+    {
+        return $this->datetime->format('H:i:s.v');
+    }
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_week.php b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_week.php
new file mode 100644
index 0000000..7711a88
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_week.php
@@ -0,0 +1,50 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use Stringable;
+
+/**
+ * Holds a year/week pair that will be stringed to something like 2011-W47
+ */
+class DatetimeValue_week extends DatetimeValue
+{
+    public static function fromString(string|Stringable|null $string): null|self
+    {
+        // null string returns null
+        if (is_null($string)) return null;
+        // try to match regular expression
+        elseif (
+            preg_match(
+                sprintf(
+                    '/^%s\-W%s$/i',
+                    static::REGEX_YEAR,
+                    static::REGEX_WEEKNUM
+                ),
+                $string,
+                $matches
+            )
+        ) {
+            return new self(
+                intval($matches['year']),
+                intval($matches['weeknum'])
+            );
+        }
+        // return null if nothing found
+        return null;
+    }
+
+    public function __construct(public int $year, public int $week)
+    {
+    }
+
+    public function __toString()
+    {
+        return sprintf(
+            '%s%04d-%02d',
+            $this->year < 0 ? '-' : '',
+            abs($this->year),
+            $this->week
+        );
+    }
+}
\ No newline at end of file
diff --git a/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_year.php b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_year.php
new file mode 100644
index 0000000..b9f85c6
--- /dev/null
+++ b/src/Html5/InlineTextSemantics/TimeTag/DatetimeValue_year.php
@@ -0,0 +1,44 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use Stringable;
+
+class DatetimeValue_year extends DatetimeValue
+{
+    public static function fromString(string|Stringable|null $string): null|self
+    {
+        // null string returns null
+        if (is_null($string)) return null;
+        // try to match regular expression
+        elseif (
+            preg_match(
+                sprintf(
+                    '/^%s$/',
+                    static::REGEX_YEAR
+                ),
+                $string,
+                $matches
+            )
+        ) {
+            return new self(
+                intval($matches['year'])
+            );
+        }
+        // return null if nothing found
+        return null;
+    }
+
+    public function __construct(protected int $year)
+    {
+    }
+
+    public function __toString()
+    {
+        return sprintf(
+            '%s%04d',
+            $this->year < 0 ? '-' : '',
+            abs($this->year)
+        );
+    }
+}
\ No newline at end of file
diff --git a/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_Test.php b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_Test.php
new file mode 100644
index 0000000..bf60054
--- /dev/null
+++ b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_Test.php
@@ -0,0 +1,64 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use PHPUnit\Framework\TestCase;
+
+class DatetimeValue_date_Test extends TestCase
+{
+    public function testFromValidStrings(): void
+    {
+        // example from mdn
+        $this->assertEquals(
+            "2011-11-18",
+            DatetimeValue_date::fromString("2011-11-18")
+                    ?->__toString()
+        );
+        // bottom of range (test zero year)
+        $this->assertEquals(
+            "0000-01-01",
+            DatetimeValue_date::fromString("0000-1-1")
+                    ?->__toString()
+        );
+        // top of range
+        $this->assertEquals(
+            "99999-12-31",
+            DatetimeValue_date::fromString("99999-12-31")
+                    ?->__toString()
+        );
+        // negative years (BCE)
+        $this->assertEquals(
+            "-1000-12-31",
+            DatetimeValue_date::fromString("-1000-12-31")
+                    ?->__toString()
+        );
+    }
+
+    public function testFromInvalidStrings(): void
+    {
+        // too short year
+        $this->assertNull(
+            DatetimeValue_date::fromString("999-1-1")
+        );
+        // below range
+        $this->assertNull(
+            DatetimeValue_date::fromString("1999-0-1")
+        );
+        $this->assertNull(
+            DatetimeValue_date::fromString("1999-1-0")
+        );
+        $this->assertNull(
+            DatetimeValue_date::fromString("1999-00-00")
+        );
+        // above range
+        $this->assertNull(
+            DatetimeValue_date::fromString("1999-13-02")
+        );
+        $this->assertNull(
+            DatetimeValue_date::fromString("1999-02-32")
+        );
+        $this->assertNull(
+            DatetimeValue_date::fromString("1999-13-32")
+        );
+    }
+}
\ No newline at end of file
diff --git a/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_month_Test.php b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_month_Test.php
new file mode 100644
index 0000000..ce0bd65
--- /dev/null
+++ b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_month_Test.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use PHPUnit\Framework\TestCase;
+
+class DatetimeValue_month_Test extends TestCase
+{
+    public function testFromValidStrings(): void
+    {
+        // example from mdn
+        $this->assertEquals(
+            "2011-11",
+            DatetimeValue_month::fromString("2011-11")
+                    ?->__toString()
+        );
+        // bottom of range
+        $this->assertEquals(
+            "0000-01",
+            DatetimeValue_month::fromString("0000-01")
+                    ?->__toString()
+        );
+        // top of range
+        $this->assertEquals(
+            "99999-12",
+            DatetimeValue_month::fromString("99999-12")
+                    ?->__toString()
+        );
+        // negative year
+        $this->assertEquals(
+            "-1500-06",
+            DatetimeValue_month::fromString("-1500-06")
+                    ?->__toString()
+        );
+    }
+}
\ No newline at end of file
diff --git a/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_time_Test.php b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_time_Test.php
new file mode 100644
index 0000000..9f69a67
--- /dev/null
+++ b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_time_Test.php
@@ -0,0 +1,56 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use PHPUnit\Framework\TestCase;
+
+class DatetimeValue_time_Test extends TestCase
+{
+    public function testFromValidStrings(): void
+    {
+        // examples from mdn
+        $this->assertEquals(
+            "14:54:00.000",
+            DatetimeValue_time::fromString("14:54")
+                    ?->__toString()
+        );
+        $this->assertEquals(
+            "14:54:39.000",
+            DatetimeValue_time::fromString("14:54:39")
+                    ?->__toString()
+        );
+        $this->assertEquals(
+            "14:54:39.929",
+            DatetimeValue_time::fromString("14:54:39.929")
+                    ?->__toString()
+        );
+        // bottom of range
+        $this->assertEquals(
+            "00:00:00.000",
+            DatetimeValue_time::fromString("00:00:00.000")
+                    ?->__toString()
+        );
+        // top of range
+        $this->assertEquals(
+            "23:59:59.999",
+            DatetimeValue_time::fromString("23:59:59.999")
+                    ?->__toString()
+        );
+    }
+
+    public function testFromInvalidStrings(): void
+    {
+        // hour too big
+        $this->assertNull(
+            DatetimeValue_time::fromString("24:00:00.000")
+        );
+        // minute too big
+        $this->assertNull(
+            DatetimeValue_time::fromString("00:60:00.000")
+        );
+        // second too big
+        $this->assertNull(
+            DatetimeValue_time::fromString("00:00:60.000")
+        );
+    }
+}
\ No newline at end of file
diff --git a/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_week_Test.php b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_week_Test.php
new file mode 100644
index 0000000..8ecfddb
--- /dev/null
+++ b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_week_Test.php
@@ -0,0 +1,48 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use PHPUnit\Framework\TestCase;
+
+class DatetimeValue_week_Test extends TestCase
+{
+    public function testFromValidStrings(): void
+    {
+        // example from mdn
+        $this->assertEquals(
+            "2011-W47",
+            DatetimeValue_week::fromString("2011-W47")
+                    ?->__toString()
+        );
+        // bottom of range
+        $this->assertEquals(
+            "0000-W01",
+            DatetimeValue_week::fromString("0000-W01")
+                    ?->__toString()
+        );
+        // top of range
+        $this->assertEquals(
+            "99999-W53",
+            DatetimeValue_week::fromString("99999-W53")
+                    ?->__toString()
+        );
+        // negative year
+        $this->assertEquals(
+            "-1500-06",
+            DatetimeValue_week::fromString("-1500-06")
+                    ?->__toString()
+        );
+    }
+
+    public function testFromInvalidStrings(): void
+    {
+        // week too small
+        $this->assertNull(
+            DatetimeValue_week::fromString("0000-W00")
+        );
+        // week too big
+        $this->assertNull(
+            DatetimeValue_week::fromString("0000-W54")
+        );
+    }
+}
\ No newline at end of file
diff --git a/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_year_Test.php b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_year_Test.php
new file mode 100644
index 0000000..a6a2b9c
--- /dev/null
+++ b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_year_Test.php
@@ -0,0 +1,44 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use PHPUnit\Framework\TestCase;
+
+class DatetimeValue_year_Test extends TestCase
+{
+    public function testFromValidStrings(): void
+    {
+        // example from mdn
+        $this->assertEquals(
+            "2011",
+            DatetimeValue_year::fromString("2011")
+                    ?->__toString()
+        );
+        // bottom of range
+        $this->assertEquals(
+            "0000",
+            DatetimeValue_year::fromString("0000")
+                    ?->__toString()
+        );
+        // top of range
+        $this->assertEquals(
+            "99999",
+            DatetimeValue_year::fromString("99999")
+                    ?->__toString()
+        );
+        // negative year with only three digits
+        $this->assertEquals(
+            "-0150",
+            DatetimeValue_year::fromString("-0150")
+                    ?->__toString()
+        );
+    }
+
+    public function testFromInvalidStrings(): void
+    {
+        // year is too short
+        $this->assertNull(
+            DatetimeValue_year::fromString("123")
+        );
+    }
+}
\ No newline at end of file
diff --git a/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_yearless_Test.php b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_yearless_Test.php
new file mode 100644
index 0000000..66f577b
--- /dev/null
+++ b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_date_yearless_Test.php
@@ -0,0 +1,54 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use PHPUnit\Framework\TestCase;
+
+class DatetimeValue_date_yearless_Test extends TestCase
+{
+    public function testFromValidStrings(): void
+    {
+        // example from mdn
+        $this->assertEquals(
+            "11-18",
+            DatetimeValue_date_yearless::fromString("11-18")
+                    ?->__toString()
+        );
+        // bottom of range
+        $this->assertEquals(
+            "01-01",
+            DatetimeValue_date_yearless::fromString("1-1")
+                    ?->__toString()
+        );
+        // top of range
+        $this->assertEquals(
+            "12-31",
+            DatetimeValue_date_yearless::fromString("12-31")
+                    ?->__toString()
+        );
+    }
+
+    public function testFromInvalidStrings(): void
+    {
+        // below range
+        $this->assertNull(
+            DatetimeValue_date_yearless::fromString("0-1")
+        );
+        $this->assertNull(
+            DatetimeValue_date_yearless::fromString("1-0")
+        );
+        $this->assertNull(
+            DatetimeValue_date_yearless::fromString("00-00")
+        );
+        // above range
+        $this->assertNull(
+            DatetimeValue_date_yearless::fromString("13-02")
+        );
+        $this->assertNull(
+            DatetimeValue_date_yearless::fromString("02-32")
+        );
+        $this->assertNull(
+            DatetimeValue_date_yearless::fromString("13-32")
+        );
+    }
+}
\ No newline at end of file
diff --git a/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_datetime_Test.php b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_datetime_Test.php
new file mode 100644
index 0000000..9d5245c
--- /dev/null
+++ b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_datetime_Test.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use PHPUnit\Framework\TestCase;
+
+class DatetimeValue_datetime_Test extends TestCase
+{
+    public function testFromValidStrings(): void
+    {
+        // example from mdn
+        $this->assertEquals(
+            "2011-11-18T14:54:39+00:00",
+            DatetimeValue_datetime::fromString("2011-11-18T14:54:39Z")
+                    ?->__toString()
+        );
+        // bottom of range
+        $this->assertEquals(
+            "0000-01-01T00:00:00-23:59",
+            DatetimeValue_datetime::fromString("0000-01-01 00:00:00-23:59")
+                    ?->__toString()
+        );
+        // top of range
+        $this->assertEquals(
+            "99999-12-31T23:59:59+23:59",
+            DatetimeValue_datetime::fromString("99999-12-31T23:59:59+23:59")
+                    ?->__toString()
+        );
+        // negative years (BCE)
+        $this->assertEquals(
+            "-1000-12-31T23:59:59+00:00",
+            DatetimeValue_datetime::fromString("-1000-12-31T23:59:59+0000")
+                    ?->__toString()
+        );
+    }
+}
\ No newline at end of file
diff --git a/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_datetime_local_Test.php b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_datetime_local_Test.php
new file mode 100644
index 0000000..58ed078
--- /dev/null
+++ b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_datetime_local_Test.php
@@ -0,0 +1,68 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use PHPUnit\Framework\TestCase;
+
+class DatetimeValue_datetime_local_Test extends TestCase
+{
+    public function testFromValidStrings(): void
+    {
+        // example from mdn
+        $this->assertEquals(
+            "2011-11-18T14:54:39.929",
+            DatetimeValue_datetime_local::fromString("2011-11-18T14:54:39.929")
+                    ?->__toString()
+        );
+        // bottom of range (test zero year)
+        $this->assertEquals(
+            "0000-01-01T00:00:00.000",
+            DatetimeValue_datetime_local::fromString("0000-01-01 00:00:00.000")
+                    ?->__toString()
+        );
+        // top of range
+        $this->assertEquals(
+            "99999-12-31T23:59:59.999",
+            DatetimeValue_datetime_local::fromString("99999-12-31T23:59:59.999")
+                    ?->__toString()
+        );
+        // negative years (BCE)
+        $this->assertEquals(
+            "-1000-12-31T23:59:59.999",
+            DatetimeValue_datetime_local::fromString("-1000-12-31T23:59:59.999")
+                    ?->__toString()
+        );
+    }
+
+    public function testFromInvalidStrings(): void
+    {
+        // too short microseconds
+        $this->assertNull(
+            DatetimeValue_datetime_local::fromString("1999-1-1T23:59:59.99")
+        );
+        // too short year
+        $this->assertNull(
+            DatetimeValue_datetime_local::fromString("999-1-1T23:59:59.999")
+        );
+        // below range
+        $this->assertNull(
+            DatetimeValue_datetime_local::fromString("1999-0-1T23:59:59.999")
+        );
+        $this->assertNull(
+            DatetimeValue_datetime_local::fromString("1999-1-0T23:59:59.999")
+        );
+        $this->assertNull(
+            DatetimeValue_datetime_local::fromString("1999-00-00T23:59:59.999")
+        );
+        // above range
+        $this->assertNull(
+            DatetimeValue_datetime_local::fromString("1999-13-02T23:59:59.999")
+        );
+        $this->assertNull(
+            DatetimeValue_datetime_local::fromString("1999-02-32T23:59:59.999")
+        );
+        $this->assertNull(
+            DatetimeValue_datetime_local::fromString("1999-13-32T23:59:59.999")
+        );
+    }
+}
\ No newline at end of file
diff --git a/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_duration_Test.php b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_duration_Test.php
new file mode 100644
index 0000000..eb8935b
--- /dev/null
+++ b/tests/Html5/InlineTextSemantics/TimeTag/DatetimeValue_duration_Test.php
@@ -0,0 +1,34 @@
+<?php
+
+namespace ByJoby\HTML\Html5\InlineTextSemantics\TimeTag;
+
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Honestly this one doesn't need a lot of testing, because it just uses PHP's
+ * DateInterval built-in parsing
+ */
+class DatetimeValue_duration_Test extends TestCase
+{
+    public function testFromValidStrings(): void
+    {
+        // example from mdn
+        $this->assertEquals(
+            "PT4H18M3S",
+            DatetimeValue_duration::fromString("PT4H18M3S")
+                    ?->__toString()
+        );
+        // bottom of range
+        $this->assertEquals(
+            "PT1S",
+            DatetimeValue_duration::fromString("PT1S")
+                    ?->__toString()
+        );
+        // all values
+        $this->assertEquals(
+            "P99Y99M99DT99H99M99S",
+            DatetimeValue_duration::fromString("P99Y99M99DT99H99M99S")
+                    ?->__toString()
+        );
+    }
+}
\ No newline at end of file