Negative Unix Timestamps: Dates Before 1970 Explained
Negative Unix timestamps represent dates that occurred before the Unix epoch on January 1, 1970. They are valid values in many systems and map directly to earlier calendar dates.
What is a negative Unix timestamp?
When epoch counters run backward from 1970-01-01 00:00:00 UTC, the numeric value becomes negative. These negative values are still measured in seconds relative to the epoch.
Examples of dates and negative values
| Date | Unix Timestamp |
|---|---|
| 1969-12-31 23:59:59 UTC | -1 |
| 1969-12-01 00:00:00 UTC | -2592000 |
| 1901-12-13 20:45:52 UTC | -2147483648 |
Language and database support
JavaScript: most modern engines support negative timestamps with new Date(-1 * 1000), but care is needed for legacy browsers.
Python: the standard library supports negative timestamps using datetime.fromtimestamp() and datetime.utcfromtimestamp() on many platforms.
MySQL: MySQL can store negative Unix timestamps if you convert them to a DATETIME using FROM_UNIXTIME(), but some older versions may behave differently for pre-1970 dates.