The text content of element “time” was not in the required format: The literal did not satisfy the time-datetime format.

The <time> element represents a specific moment or duration in time. Browsers, search engines, and assistive technologies rely on parsing its value to understand temporal data programmatically. The element can get its machine-readable value from two places: the datetime attribute, or, if that attribute is absent, from the element’s text content directly.

When there is no datetime attribute, the text content itself must be in one of the valid formats specified by the HTML standard. This is where the error typically occurs—authors write a human-readable date like “March 20, 2025” or “last Tuesday” as the text content without providing a datetime attribute, and the validator rejects it because that string isn’t machine-parsable.

Why This Matters

• Machine readability: Search engines (via structured data) and browser features (like calendar integration) depend on parsing the <time> element’s value. An invalid format means these tools can’t understand the date or time.
• Accessibility: Screen readers and other assistive technologies may use the machine-readable datetime to present temporal information more helpfully to users.
• Standards compliance: The HTML specification explicitly defines which formats are valid. Using anything else makes your document non-conforming.

How to Fix It

You have two options:

1. Add a datetime attribute with the machine-readable value, and keep the human-readable text as the visible content. This is the most common and practical approach.
2. Use a valid format directly as the text content if you don’t mind displaying a machine-readable format to users.

Valid Formats

Here is a reference of accepted formats for the <time> element:

Examples

Incorrect: Human-readable text without datetime attribute

The validator will report the error because “March 20, 2025” is not a valid machine-readable format:

<p>The concert is on <time>March 20, 2025</time>.</p>

Incorrect: Informal text as content

Similarly, casual date strings are not valid:

<p>Updated <time>last Friday</time>.</p>

Correct: Using the datetime attribute

Add a datetime attribute with the machine-readable value and keep the human-friendly text visible:

<p>The concert is on <time datetime="2025-03-20">March 20, 2025</time>.</p>

Correct: Including time and timezone

<p>
  The event starts at
  <time datetime="2025-03-20T13:00-05:00">1:00 PM EST on March 20, 2025</time>.
</p>

Correct: Machine-readable format as text content

If no datetime attribute is provided, the text content itself must be a valid format:

<p>Date: <time>2025-03-20</time></p>

Correct: Representing a duration

<p>Cooking time: <time datetime="PT1H30M">1 hour and 30 minutes</time>.</p>

Correct: Using just a time value

<p>The shop opens at <time>09:00</time> every day.</p>

As a general rule, whenever you want to display a date or time in a natural, human-friendly way, always pair it with a datetime attribute that contains the machine-readable equivalent. This keeps your HTML valid, your content accessible, and your temporal data useful to machines.

Learn more:

MDN Reference

MDN - time

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MDN Reference

MDN - date and time formats

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WHATWG Spec

HTML spec - valid duration string

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