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RFC 3339 / INTERNET TIMESTAMPS

Read a complete timestamp

01

A timestamp identifies an instant. RFC 3339 defines a restricted ISO 8601 date/time format using the Gregorian calendar and an explicit relation to UTC, Coordinated Universal Time.

DIAGRAMRead RFC section 5.6 ↗
RFC 3339 · § 5.6EXAMPLE
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Read a complete timestampThe published timestamp 1985-04-12T23:20:50.52Z is first one literal, then date fields (year 1985, month 04, day 12), then clock fields (23 hours, 20 minutes, 50 seconds), fraction .52 and zero offset Z. The last view compares permitted lowercase t/z with recommended generated uppercase T/Z. It describes one instant, not a geographic time zone. Chapter 3 explains the updated local-offset meaning of Z.RFC 3339 · published timestamp exampleAllowed in base grammar:1985-04-12t23:20:50.52zgenerated spelling SHOULD use uppercase1985-04-12T23:20:50.52ZA using specification MAY require uppercaseAppendix A is wider ISO syntax, not this profile
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Accept permitted case while generating clear output.

The base grammar also permits 1985-04-12t23:20:50.52z. Uppercase T and Z are the recommended generated spelling; lowercase does not automatically make a base-profile timestamp invalid.

Source for this drawing: RFC 3339 · Read RFC section 5.6 ↗

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KEY POINT

Keep the date, time and offset together.

  • A full timestamp uses four-digit year-month-day, T, hour:minute:second, an optional decimal fraction, and Z or a signed hour:minute offset. Internet protocols MUST generate four-digit years.
  • The fractional part is a dot followed by one or more digits. Date and clock separators and seconds are present in the §5.6 date-time grammar. This is a profile, not every ISO 8601 representation.
  • T and Z may be lowercase in the base grammar. Generators SHOULD use uppercase; a specification using case-sensitive environments MAY require uppercase. New Internet protocols SHOULD use this profile.
DETAILS

The published example 1985-04-12T23:20:50.52Z identifies an instant with 52 hundredths of a second. The main profile is §5.6, not the wider collected ISO grammar in Appendix A. Its note permits applications to specify another date/time separator for readability, while held erratum5783 records ambiguity; this guide’s literal examples use T/t and do not silently declare every space-separated string part of the base ABNF. Date-only values may be used by other application contracts, but are not complete date-time timestamps.

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