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📆 Datetime

Various datetime formats at a glance.

tip
  1. Store datetimes as UTC in databse and convert to local time when displaying to users.
  2. Timezone is not a part of a datetime or timestamp. To store timezone information, it should be record in a seperate field. See Timezone
  3. Use _on for date, and _at for time
  4. Do not attemp to self-hack datetime computation. Use libraries.

ISO 8601 / RFC 3339​

The goto option, atively supported by JavaScript. They are quite similar but have subtle differences. Check RFC 3339 vs ISO 8601 for comprehensive examples.

Most common format that works for JSON are:

  • Datetime: %Y-%M-%DT%h:%m:%s%Z:%z
    • 2021-01-01T13:00:00Z
    • 2021-01-01T13:00:00+00:00
    • 2021-01-01T13:00:00-05:00
  • Date: %Y-%M-%D
    • 2021-01-01
  • Time: %h:%m:%s%Z:%z
    • 13:00:00Z
  • Periods: Use ISO 8601
    • P1Y1M1DT1H1M1S
  • Range / Interval: Use seperate fields for start and end

RFC 9557 is an updated version of RFC 3339 published in April 2024.

RFC 2822​

Used in email headers

Format: Day, DD Mon YYYY HH:MM:SS +0000

Examples:

  • Fri, 01 Jan 2021 00:00:00 +0000
  • Fri, 01 Jan 2021 00:00:00 -0500

Unix Timestamp​

Number of seconds since 1970-01-01 00:00:00 UTC

Examples:

  • 1609459200 (2021-01-01 00:00:00 UTC)
warning

JavaScript use miliseconds by default!

e.g.

  • Math.floor(Date.now() / 1000)
  • new Date(timestamp * 1000)

References​