Date Format Converter

Updated August 20, 2026

Date format converter online. Get ISO, RFC 2822, Unix, Excel serial, and more from one date. Free date format tool.

iso	2026-08-29T22:01:08.756Z
rfc2822	Sat, 29 Aug 2026 22:01:08 GMT
unix	1788040868
unixMs	1788040868756
excel	46263.917462
isoWeek	2026-W35
local	2026-08-29 22:01:08.756
utc	2026-08-29 22:01:08.756
relative	now

Features

One instant in ISO, RFC 2822, Unix s/ms, Excel serial, ISO week, locale strings
Pick a display time zone
Copy each field
Good cheat sheet when an API wants a weird format

Common Use Cases

Fill an HTTP Date header (RFC 2822-ish UTC)
Get Excel serial for a spreadsheet formula
Read ISO week number
Compare locale vs UTC strings
Produce Unix ms for JS Date

Formats are projections of one instant

Excel serials are days since 1899-12-30 with leap-year quirks in desktop Excel. We use the common 25569 offset for Unix day conversion, which matches Sheets for modern dates. ISO week is UTC-based here.

Examples

Valid - now

now

Frequently Asked Questions

Is Excel serial exact for 1900?

Excel’s 1900 leap-year bug is not fully emulated. Use this for dates after 1900 that you already trust as Unix instants.

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Unix timestamp

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ISO 8601

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Tips

HTTP Date is UTC. Do not send a local RFC 2822 to caches.