Unix Timestamps Explained What They Are and How to Convert Them

What Is a Unix Timestamp

A Unix timestamp is the number of seconds elapsed since January 1, 1970 at exactly 00:00:00 UTC. That specific moment is called the Unix epoch. It was chosen during the development of Unix operating systems in the late 1960s and has remained the standard since.

As of early 2026, the current Unix timestamp is around 1,750,000,000, meaning roughly 1.75 billion seconds have passed since the epoch. This number increments by exactly one every second without exception.

Millisecond timestamps, used in JavaScript and many modern systems, are 1,000 times larger. A timestamp like '1704067200000' with three trailing zeros indicates milliseconds. Divide by 1,000 to get seconds.

Why Developers Prefer Timestamps Over Date Strings

Timestamps are timezone-neutral. The Unix timestamp 1704067200 represents the same absolute moment in time regardless of whether a server is in New York, London or Tokyo. There is no ambiguity about which timezone applies.

Storing a date-time string like "2024-01-01 12:00:00" without timezone information creates a class of bug that is painful to debug. Was that noon UTC? Noon Eastern? Noon in the developer's local time? Timestamps eliminate this entire category of problem.

Timestamps are simple to compare and calculate. To check if event A happened before event B, compare their timestamps. To find all events in the last seven days, subtract 604,800 seconds from the current timestamp and filter. Pure arithmetic with no calendar logic required.

Timestamps are compact. A 10-digit integer is smaller than a formatted date string and sorts correctly without any special handling.

The 2038 Problem

Unix timestamps stored as 32-bit signed integers hit their maximum value at 2,147,483,647, which corresponds to January 19, 2038 at 03:14:07 UTC. After that second, 32-bit systems that have not been updated will roll over to a large negative number representing December 13, 1901.

Most modern systems use 64-bit integers which extend the range by hundreds of billions of years. Embedded systems and legacy software may still be affected and need attention before 2038.

Common Timestamp Formats

Unix seconds are 10 digits as of 2026. Unix milliseconds are 13 digits, used by JavaScript's 'Date.now()' and many modern APIs.

ISO 8601 format looks like '2024-01-01T00:00:00Z' where the Z explicitly indicates UTC. This is the international standard and the preferred format for human-readable timestamps in APIs.

SQL DateTime looks like '2024-01-01 00:00:00' and is common in databases. Often timezone-naive unless the column explicitly stores timezone information.

Converting Timestamps Quickly

Our Timestamp Converter accepts any format including Unix seconds, milliseconds, ISO 8601 and plain date strings, converting to all formats simultaneously. It shows the timestamp across 23 world timezones, plus the day of week, week number and quarter.

Paste a raw number from an API response or log file and immediately see the human-readable date and time it represents across all relevant timezones.