Unix Timestamp Converter

About this tool

Unix timestamps count elapsed time from 1 January 1970 UTC and are common in APIs, logs, databases and authentication claims. The Timestamp Converter converts seconds or milliseconds into readable UTC and local dates, and can turn a date-time value back into both timestamp units.

The main source of timestamp mistakes is not arithmetic but interpretation: a ten-digit value is usually seconds, a thirteen-digit value is usually milliseconds, and an entered date without a timezone may be interpreted in the browser's local zone. Always record the expected unit and timezone in an API contract. When inspecting token expiry claims, the JWT Expiry Checker provides token-specific context.

How to use it

1. Select timestamp-to-date or date-to-timestamp mode.
2. Paste the value and choose seconds, milliseconds or automatic unit detection.
3. Run the conversion and compare the UTC and local representations.
4. For a date input, include an explicit timezone when the source is not local time.
5. Copy the required format and document its unit in code or API schemas.

Useful ways to apply it

• Reading creation, update and expiry values returned by an API.
• Converting log timestamps while investigating an incident.
• Checking whether a value is in seconds or milliseconds.
• Preparing a future timestamp for a test fixture or scheduled event.
• Comparing UTC with the browser's local timezone display.