Bad value X for attribute “datetime” on element “time”: The literal did not satisfy the time-datetime format.

The <time> HTML element represents a specific period in time or a duration. Its datetime attribute translates human-readable text into a machine-readable format, enabling browsers, search engines, and assistive technologies to reliably parse and understand temporal data. When the datetime value doesn’t match one of the accepted formats, the machine-readable purpose of the element is defeated — tools cannot interpret the date or time, which undermines features like search engine rich results, calendar integration, and accessibility enhancements for screen readers.

The HTML specification defines several valid formats for the datetime attribute. Here are the most commonly used ones:

Format	Example	Description
Date	2024-03-15	Year, month, day
Month	2024-03	Year and month only
Year	2024	Valid year
Yearless date	03-15	Month and day without year
Time	14:30 or 14:30:00	Hours and minutes (seconds optional)
Date and time	2024-03-15T14:30	Date and time separated by T
Date and time with timezone	2024-03-15T14:30Z or 2024-03-15T14:30+05:30	With UTC (Z) or offset
Duration (precise)	PT1H30M	ISO 8601 duration
Duration (approximate)	P2Y6M	Years, months, etc.
Week	2024-W12	ISO week number

Common mistakes that trigger this error include:

• Using slashes instead of hyphens: 03/15/2024 instead of 2024-03-15
• Using informal date formats: March 15, 2024 or 15-03-2024
• Omitting the T separator between date and time: 2024-03-15 14:30
• Using 12-hour time with AM/PM: 2:30 PM instead of 14:30
• Providing incomplete values: 2024-3-5 instead of 2024-03-05 (months and days must be zero-padded)

Examples

Invalid: Slash-separated date

<time datetime="03/15/2024">March 15, 2024</time>

Valid: ISO 8601 date format

<time datetime="2024-03-15">March 15, 2024</time>

Invalid: Missing T separator and using AM/PM

<time datetime="2024-03-15 2:30 PM">March 15 at 2:30 PM</time>

Valid: Date-time with T separator and 24-hour time

<time datetime="2024-03-15T14:30">March 15 at 2:30 PM</time>

Invalid: Informal time string

<time datetime="half past two">2:30 PM</time>

Valid: Simple time value

<time datetime="14:30">2:30 PM</time>

Invalid: Non-standard duration

<time datetime="1 hour 30 minutes">1.5 hours</time>

Valid: ISO 8601 duration

<time datetime="PT1H30M">1.5 hours</time>

Valid: Date-time with timezone offset

<p>The event starts at <time datetime="2024-03-15T14:30-05:00">2:30 PM ET on March 15</time>.</p>

Valid: Using only the month

<p>Published in <time datetime="2024-03">March 2024</time>.</p>

Remember that the human-readable text content between the <time> tags can be in any format you like — it’s only the datetime attribute value that must follow the specification. This lets you display dates in a user-friendly way while still providing a standardized machine-readable value.

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