Unix Timestamp Converter

What is a Unix timestamp?

A Unix timestamp (also called epoch time or POSIX time) is the number of seconds elapsed since January 1, 1970, 00:00:00 UTC — the Unix Epoch. It is used universally in programming to represent a specific moment in time without timezone ambiguity. For example, timestamp 1700000000 = November 14, 2023, 22:13:20 UTC.

What is the difference between seconds and milliseconds?

Unix time is traditionally measured in seconds. JavaScript's Date.now() returns milliseconds (1000× larger). A 10-digit number is seconds (e.g. 1700000000); a 13-digit number is milliseconds (e.g. 1700000000000). This tool auto-detects which format you entered based on the digit count. Databases and server-side languages typically use seconds; JavaScript and many web APIs use milliseconds.

What is the Unix Epoch (January 1, 1970)?

The Unix Epoch is the reference point for all Unix timestamps — midnight UTC on January 1, 1970. It was chosen by early Unix developers as a convenient starting point. Timestamps before this date are negative numbers. The date was not historically significant; it was an arbitrary choice made when Unix was being created.

What is the Year 2038 problem?

Systems that store Unix timestamps as 32-bit signed integers max out at 2,147,483,647 — which corresponds to January 19, 2038. After that, the counter overflows to a negative number. Modern systems use 64-bit integers, which can represent dates billions of years in the future.

How do I get the current Unix timestamp in code?

JavaScript: Math.floor(Date.now() / 1000) for seconds, Date.now() for ms. Python: import time; int(time.time()). PHP: time(). Go: time.Now().Unix(). Java: System.currentTimeMillis() / 1000L. Shell: date +%s. SQL (PostgreSQL): EXTRACT(EPOCH FROM NOW())::INTEGER. SQL (MySQL): UNIX_TIMESTAMP().

Why do different timezones show different dates for the same timestamp?

Unix timestamps are always in UTC — they represent an absolute moment, with no timezone embedded. When displayed as a human date, the timestamp is converted to the local timezone of the display system. The same timestamp is always the same moment everywhere, but shows different clock times and potentially different dates depending on timezone offset.