What this converter does
Dates are written differently around the world, and the same digits can mean different days. 03/04/2026 is March 4 in the US but 3 April in most of Europe. This converter reads the date, tells you which format it recognized, flags it when it's ambiguous, and writes it out as ISO 8601, US, European, long form, a Unix timestamp, an ISO week date and an ordinal date.
Formats it reads
| Format | Example |
|---|---|
| ISO 8601 | 2026-10-27, 2026-10-27T14:30:00Z |
| Compact ISO | 20261027 |
| US, month first | 10/27/2026, 10-27-26 |
| European, day first | 27/10/2026, 27.10.2026 |
| Long form | October 27, 2026; Tue, Oct 27th 2026; 27 October 2026 |
| Unix time | 1793059200 (seconds) or 1793059200000 (milliseconds) |
How ambiguity is detected
For a numeric date like a/b/yyyy, if one number is over 12 it must be the day, so there's only one reading. If both are 12 or less and they differ, the date is ambiguous. The converter then uses your choice under "Read numeric dates as". On Auto, slashes are read the US way and dots the European way, and the other reading is shown too.
Two-digit years follow the POSIX rule used by many programs: 69 to 99 mean 1969 to 1999, and 00 to 68 mean 2000 to 2068. The IETF's RFC 3339 says Internet protocols must use four-digit years, and writing them avoids the guesswork.
How Unix time works
Unix time counts seconds since the Epoch, which POSIX defines as 00:00:00 UTC on January 1, 1970. Every day counts as exactly 86,400 seconds, so leap seconds are ignored.
Worked example
October 27, 2026 is 20,753 days after January 1, 1970. 20,753 × 86,400 = 1,793,059,200, the Unix timestamp for midnight UTC that day. Going the other way, 1,700,000,000 seconds is November 14, 2023 at 22:13:20 UTC.
Numbers with 12 or more digits are read as milliseconds, which is what JavaScript and many APIs use.
Limitations
- A date without a time converts to a timestamp at midnight in the chosen zone (UTC by default).
- Dates before 1970 give negative timestamps. Years before 1582 use the Gregorian calendar extended backward.
- Very loose text like "next Tuesday" isn't understood. Use the date calculator for that.
Sources
- IETF RFC 3339: Date and Time on the Internet (ISO 8601 profile, week-date syntax, four-digit years)
- POSIX (The Open Group): Seconds Since the Epoch and the definition of the Epoch
- POSIX strptime() (the 69–99 / 00–68 two-digit year rule)