Unix Timestamp to Date Calculator
Convert a Unix timestamp in seconds or milliseconds to a readable UTC date and time, with the ISO 8601 string and weekday.
How it works
date = the Unix epoch (1970-01-01 00:00:00 UTC) + the timestamp · seconds are multiplied by 1,000 to milliseconds before conversion · the result is shown in UTC
A Unix timestamp is the number of seconds (or milliseconds) since midnight UTC on January 1, 1970. Adding that many seconds to the epoch gives the exact instant, which this tool renders as a UTC calendar date and time plus the ISO 8601 string used across the web and in databases. Ten-digit values are usually seconds; thirteen-digit values are milliseconds — pick the matching unit so the year comes out sensibly rather than stuck near 1970 or far in the future.
Worked example
The timestamp 1,789,600,000 seconds converts to Wednesday, September 16, 2026 at 23:06:40 UTC — its ISO form is 2026-09-16T23:06:40.000Z.
Sources: Unix time — Wikipedia
Frequently asked questions
How do I tell seconds from milliseconds?
A current timestamp in seconds is about 10 digits (around 1.7 billion); in milliseconds it is about 13 digits. If your converted date lands near 1970 you probably have milliseconds set to seconds, or vice versa.
Why is the result in UTC?
Unix time is defined in UTC, with no time zone of its own. Showing UTC keeps the conversion unambiguous; to get your local time, add or subtract your zone’s offset from the UTC value shown.
What is the 2038 problem?
Systems that store the timestamp as a signed 32-bit integer overflow just after 03:14:07 UTC on January 19, 2038. Modern 64-bit time types remove that limit, so timestamps well beyond 2038 convert correctly here.
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This calculator is for educational purposes. Double-check important results before acting on them.