ISO 8601

The ISO 8601 standard defines formats for representing date-time values as text.

• The T is just a marker for where the time part begins.
• The Z is an abbreviation of +00:00, meaning UTC (an offset of zero hour-minutes-seconds). Pronounced “Zulu” per military and aviation tradition.

From the Wikipedia article on ISO 8601

A single point in time can be represented by concatenating a complete date expression, the letter T as a delimiter, and a valid time expression. For example “2007-04-05T14:30”.

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If the time is in UTC, add a Z directly after the time without a space. Z is the zone designator for the zero UTC offset. “09:30 UTC” is therefore represented as “09:30Z” or “0930Z”. “14:45:15 UTC” would be “14:45:15Z” or “144515Z”.