Unix Timestamp Converter — Epoch to Date & Date to Epoch

A Unix timestamp (also called epoch time or POSIX time) is the number of seconds that have elapsed since January 1, 1970 at 00:00:00 UTC. It is timezone-independent: 1718445600 means the same moment everywhere on Earth. That property is why backend systems, APIs, and databases store timestamps as Unix integers rather than formatted date strings — there is no ambiguity about DST offsets, locale conventions, or timezone names.

This converter handles both directions. Epoch to date: paste a Unix timestamp and get the UTC date, your local date and time, the ISO 8601 representation, and the relative age ("3 days ago"). Date to epoch: pick a date, time, and timezone using the date picker and get the corresponding Unix timestamp to copy into code, a configuration file, or an API call. Everything runs in the browser.

Seconds, milliseconds, and microseconds — how to tell them apart

The number of digits is the signal. For dates in the 2020s:

• 10 digits — seconds (e.g., 1718445600). Standard for Unix time; used by POSIX APIs, most Linux tools, JWT exp/iat claims, HTTP headers like Retry-After.
• 13 digits — milliseconds (e.g., 1718445600000). JavaScript's Date.now(), Java's System.currentTimeMillis(), most browser APIs.
• 16 digits — microseconds. PostgreSQL's EXTRACT(EPOCH FROM now()) * 1000000, Python's time.time_ns() // 1000.

This tool auto-detects the unit from the digit count and labels which it's treating the input as. If your 13-digit timestamp produces a date in 2025, it's in milliseconds and being correctly detected.

Date to epoch — when you need this direction

Setting a JWT exp claim, writing a cache expiry, scheduling a cron job, or constructing an API request that accepts a Unix timestamp in the body: these all require converting a target date into epoch format. Select the date and time using the picker, choose the timezone (or leave as UTC to get the timezone-independent value), and copy the resulting epoch integer. For JWT expiry: take the current epoch plus the number of seconds in your intended validity period (86400 for 24 hours, 604800 for 7 days).

The Year 2038 problem

32-bit signed integers max out at 2147483647, which is January 19, 2038 at 03:14:07 UTC. Systems that store Unix timestamps in a 32-bit int field will overflow on that date — either wrapping to a large negative number (representing a 1901 date) or throwing an overflow error depending on the language and runtime. Modern systems use 64-bit integers, which won't overflow until the year 292,277,026,596. If your system stores epoch values in a legacy 32-bit field and serves anything scheduled past 2038, that's a live bug.

ISO 8601 and UTC vs local time

The epoch-to-date direction outputs three time representations: UTC (2024-06-15 12:00:00 UTC), your browser's local time with the detected timezone offset, and ISO 8601 format (2024-06-15T12:00:00Z). ISO 8601 with the trailing Z is the standard for API interchange — it's unambiguous and parseable by all date libraries in all languages. The local time output is for human reading; use ISO 8601 or raw epoch for machine consumption.