What is a Unix timestamp?
A Unix timestamp represents an instant as elapsed time since 00:00:00 UTC on January 1, 1970, commonly called the Unix epoch. Software uses epoch values because numbers are easy to store, compare, sort, and exchange between systems.
Seconds versus milliseconds
Traditional Unix time is measured in seconds, while JavaScript and many APIs use milliseconds. A millisecond value is usually about 1,000 times larger. Auto-detection handles typical modern dates, and the explicit unit selector removes ambiguity for unusual values.
UTC, local time, and ISO 8601
The timestamp itself does not contain a timezone. UTC shows the shared global instant, local time applies the timezone configured in your browser, and ISO 8601 provides a standardized UTC representation ending in Z.
Common timestamp uses
Convert values found in APIs, databases, logs, JWT claims, scheduled jobs, analytics exports, or debugging output. When converting a local date, remember that daylight-saving rules and the browser timezone affect the resulting instant.