What's the difference between ISO 8601 and RFC 3339 Date Formats?

datetime format web-standards
Brig Lamoreaux picture Brig Lamoreaux · Feb 6, 2009 · Viewed 159.1k times · Source

ISO 8601 and RFC 3339 seem to be two formats that are common the web. Should I use one over the other? Is one just an extension? Do I really need to care that bad?

Answer

ConroyP picture ConroyP · Feb 6, 2009

Is one just an extension?

Pretty much, yes - RFC 3339 is listed as a profile of ISO 8601. Most notably RFC 3339 specifies a complete representation of date and time (only fractional seconds are optional). The RFC also has some small, subtle differences. For example truncated representations of years with only two digits are not allowed -- RFC 3339 requires 4-digit years, and the RFC only allows a period character to be used as the decimal point for fractional seconds. The RFC also allows the "T" to be replaced by a space (or other character), while the standard only allows it to be omitted (and only when there is agreement between all parties using the representation).

I wouldn't worry too much about the differences between the two, but on the off-chance your use case runs in to them, it'd be worth your while taking a glance at:

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