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RFC 3339 Converter

Convert an RFC 3339 timestamp to Unix time, or a Unix timestamp to RFC 3339.

RFC 3339 to Unix time

Unix time to RFC 3339

What is RFC 3339?

RFC 3339 is the date-time format defined for internet protocols: a full date, a full time with seconds, and a mandatory UTC offset (either Z for UTC or a signed +hh:mm). It is a stricter subset of ISO 8601, which allows several optional parts that RFC 3339 requires, so every RFC 3339 string is valid ISO 8601 but not the reverse.

Where you will see it

Many JSON APIs, log formats and configuration files specify RFC 3339 explicitly because it removes the ambiguity that plain ISO 8601 allows (such as a date with no time, or a time with no offset). This tool converts it to and from Unix time and shows the offset that was used.

Want the background? Read our comprehensive guide: ISO 8601 Date and Time Format.

How to use this tool

To convert RFC 3339 to Unix time: paste the timestamp and select Convert to Unix.
To convert Unix time to RFC 3339: enter the timestamp, choose UTC or a local offset, and select Convert to RFC 3339.
Copy the result you need.
Select Use example to see a worked RFC 3339 string with an offset.

Examples

An RFC 3339 timestamp with an offset, converted to Unix time and back.

RFC 3339 to Unix

2026-09-20T14:30:00+02:00

Unix seconds: 1789907400

Unix to RFC 3339 (UTC)

1789907400

RFC 3339: 2026-09-20T12:30:00Z

Unix to RFC 3339, Tokyo offset

1789907400

RFC 3339: 2026-09-20T21:30:00+09:00

Frequently Asked Questions

Is RFC 3339 the same as ISO 8601?

RFC 3339 is a stricter profile of ISO 8601. Every valid RFC 3339 string is also valid ISO 8601, but ISO 8601 allows some forms, such as a date without a time, that RFC 3339 does not.

Is the UTC offset required?

Yes. Unlike plain ISO 8601, RFC 3339 always requires either Z (UTC) or a signed offset such as +02:00; a string without one is rejected with an explanation.

Does it support leap seconds?

No. RFC 3339 technically allows a leap second (:60), but Unix time does not represent them, so this tool does not accept a :60 seconds value.

What is the difference from RFC 2822?

RFC 2822 is the older email and HTTP header date format (Mon, 21 Sep 2026 14:13:20 +0000). RFC 3339 is the newer, sortable format most JSON APIs use today. Use the Date Format Converter if you need to convert between the two.