Unix timestamp converter
Convert Unix seconds or milliseconds to UTC dates, or UTC dates to timestamps.
UTC only. Integers for timestamps; ISO input must end in Z. Fractional seconds in ISO input are limited to milliseconds.
Runs in your browser. Inputs are not uploaded or saved.
How to use
Choose a mode, enter values or load the example, then copy or download your result.
Rules and worked example
Unix time counts from 1970-01-01T00:00:00Z. The example 1704067200 seconds is 2024-01-01T00:00:00.000Z. Select the unit explicitly: the tool never guesses from digit count. Negative timestamps represent dates before the epoch.
Questions and answers
How are fractional seconds and time zones handled?
Enter UTC ISO dates ending in Z, with seconds and an optional one to three millisecond digits. Local times and offset strings are intentionally rejected to avoid ambiguity. Millisecond output is exact; seconds output floors toward negative infinity. Unix time does not model leap seconds, and this converter supports calendar years 0001–9999.