Unix Timestamp Converter

What each Convert button prints

The numeric Convert trims the field and accepts an optional leading minus and one decimal point. Auto-detect treats a magnitude below 100 billion as seconds and multiplies by 1,000. Anything at or above 100 billion stays milliseconds. Seconds and Milliseconds in the unit menu skip that test. The date is new Date of the resulting milliseconds. Date output is three lines: UTC from toUTCString, ISO 8601 from toISOString, and Local from toLocaleString. For 1700000000000 the UTC line is Tue, 14 Nov 2023 22:13:20 GMT and the ISO line is 2023-11-14T22:13:20.000Z. The status says Converted successfully. Interpreted as milliseconds. The same digits with the unit set to Seconds are a different century, because the page then multiplies by 1,000.

The date Convert trims the field and calls the JavaScript date parser. A failed parse says Could not parse date. Try ISO 8601 format (e.g. 2024-01-15T12:00:00Z). A success prints Seconds (Unix) as the milliseconds divided by 1,000 and rounded down, then Milliseconds as the full getTime value. 2023-11-14T22:13:20Z is 1700000000 and 1700000000000. A fractional instant such as 2023-11-14T22:13:20.500Z keeps 500 on the millisecond line and still floors the seconds line. The status on this button is Converted successfully. with no unit sentence. Local on the other result uses the browser timezone and locale, so the same UTC instant can read 10:13:20 PM in a UTC en-US browser and an hour later or earlier somewhere else. UTC and ISO do not move.

The unit menu, Use current time, and the two buttons

Timestamp unit offers Auto-detect, Seconds, and Milliseconds. The hint under the menu repeats the cutoff: magnitudes below 100 billion are seconds. The menu does not change a result already on screen. Press Convert again after you change it. Use current time writes Math.floor of Date.now divided by 1,000 into the numeric field and the current ISO string into the date field. You still choose which Convert to press. If the clock is five minutes fast, both fields are five minutes fast. Load sample writes the fixed pair and leaves the unit menu alone. Reset empties the fields and both result panes.

There are two controls named Convert. The first reads the numeric field. The second reads the date field. Copy output and Download output keep a single string, the last success. A later click replaces that string even if the other pane still shows its older lines. The download file is timestamp-converter.txt. An empty numeric field says Please enter a Unix timestamp. and does not clear a previous date result on screen, but it also does not become the copied text. A value that fails the number pattern, is not finite, or lands beyond 8.64e15 milliseconds says Invalid timestamp. Enter a Unix epoch value in seconds or milliseconds.

When an epoch value is the time you have

Use the numeric field when a log, a database column, or an API body already stores time since 1970-01-01T00:00:00Z. A 10-digit value around 1700000000 is seconds. A 13-digit value around 1700000000000 is milliseconds. Printing both forms from a date you trust is the other button, which is the check when a producer and a consumer disagree about the scale. The cron parser previews the next runs of a five-field schedule. It does not turn a single epoch number into a calendar line. This page does not evaluate a cron expression.

A UUID version 7 and a ULID also carry a millisecond time, packed into the identifier rather than printed as a decimal. The UUID v7 generator and the ULID generator decode those spellings. Pasting a ULID into this numeric field will not yield its embedded time. A longer comparison of those identifiers is in UUID v4 vs UUID v7 vs ULID. This page only converts a number and a date string.

The 100-billion cutoff and dates without a zone

100 billion milliseconds is 1973-03-03T09:46:40.000Z. Auto-detect therefore treats every smaller magnitude as seconds, including a millisecond timestamp from 1970, 1971, or 1972. 99999999999 is seconds. 100000000000 is milliseconds. A negative magnitude uses the same absolute-value test, so -1 is one second before the epoch and prints 1969-12-31T23:59:59.000Z when the unit is Auto-detect or Seconds. Historical millisecond values need the Milliseconds choice. A modern 13-digit value does not.

Prefer a date that ends in Z or an explicit offset. 2023-11-14, date only, is UTC midnight in current JavaScript, which is 1700000000 seconds only if you wanted the start of that UTC day. A string such as 14 Nov 2023 22:13:20 with no zone is interpreted in the browser's local zone, and the seconds you copy will shift if you open the page somewhere else. The page does not add leap seconds. Unix time and JavaScript Date skip them, so a leap-second instant is not a separate row. The copied text is the three lines or the two lines from the last Convert, not both directions at once.

Rules and limitations

Auto-detect: absolute value below 100,000,000,000 means seconds. Seconds always multiplies by 1,000. Milliseconds does not. The numeric result is UTC, ISO 8601, and Local. The date result is floored seconds and full milliseconds. Range stops past 8.64e15 milliseconds.

Use current time and Load sample fill fields only. Each Convert replaces the copied text. Local follows the browser zone and locale. A date with no zone can shift. Leap seconds are not distinct instants.

Common problems

If a 13-digit value landed in the year 50000s, Timestamp unit is Seconds. Switch to Milliseconds or Auto-detect and press Convert again.

If two browsers disagree on the seconds for the same pasted date, the string has no Z or offset. Add one. If Local looks an hour off, that line is the browser zone. Read ISO 8601 for the absolute instant.

Frequently asked questions

About this tool

Maintained by Toolbench. For large or deeply nested files, split the input into smaller batches and verify representative results before using them in an import or application. Report reproducible problems through Contact.