A raw number like 1735689600 means nothing to a human, but it's exactly how most computer systems internally represent a moment in time. This tool converts a Unix timestamp into a readable date and back again.
Counting seconds from a deliberately chosen, arbitrary moment
The Unix timestamp (also called Unix time or Epoch time) counts the number of seconds that have elapsed since midnight UTC on January 1, 1970 — a reference point, the "Unix Epoch," chosen somewhat arbitrarily by early Unix developers at Bell Labs simply as a convenient, round starting point for the operating system's internal clock representation, not for any deeper significance. Representing time as a single, ever-increasing integer rather than a structured date made time-based arithmetic (comparing two moments, calculating a duration, sorting events chronologically) dramatically simpler for early computer systems than parsing and manipulating human-readable date strings would have been — a design decision so effective that Unix time became the de facto standard timestamp representation across operating systems, databases and programming languages far beyond Unix itself.
How the conversion works
Converting a Unix timestamp to a readable date involves adding the timestamp's second count to the Epoch reference date, then formatting the result according to standard calendar and calendar rules (accounting for leap years, and, if needed, converting to a specific time zone from the timestamp's inherently time-zone-agnostic UTC baseline); the reverse conversion calculates the number of seconds elapsed between the Epoch and your specified date and time.
Where working with Unix timestamps is unavoidable
- Debugging API responses and database records — many APIs and databases store and return timestamps as raw Unix time, requiring conversion to understand what actual date and time a given record represents.
- Log file analysis — server and application logs frequently timestamp each entry using Unix time for compactness and easy chronological sorting, needing conversion for human review.
- Setting expiration times programmatically — session tokens, cache entries and JWT expiration claims are commonly expressed as Unix timestamps, and converting between a human-friendly date and the corresponding timestamp is a routine development task.
- Working across time zones consistently — because Unix time is inherently UTC-based with no embedded time zone, it's a reliable, unambiguous way to store and compare timestamps across systems operating in different regions, converted to local time only for display.
Frequently asked questions
Why do some Unix timestamps look like huge 13-digit numbers instead of 10 digits? Some systems, particularly JavaScript's built-in Date object, use milliseconds since the Epoch instead of seconds — a 13-digit timestamp is 1,000 times larger than the equivalent 10-digit seconds-based timestamp, and confusing the two is a common source of "the date is way in the future or past" bugs.
What is the "Year 2038 problem"? Many older systems store Unix timestamps as a 32-bit signed integer, which will overflow (run out of representable values) at 03:14:07 UTC on January 19, 2038 — a real, documented issue analogous to the Y2K bug, prompting a gradual industry-wide shift to 64-bit timestamp storage to avoid it.
Does a Unix timestamp include time zone information? No — a Unix timestamp always represents an absolute moment in UTC with no embedded time zone at all, which is precisely its advantage for unambiguous storage and comparison; converting it to a specific local time (like "3pm in Tokyo") is a separate, additional step applied only when displaying the value to a person.
Further reading
Wikipedia — Unix time — Full history of the Unix Epoch and the Year 2038 problem affecting 32-bit timestamp storage.