Unix Timestamp Converter

How Epoch Time Counts a Moment

A Unix timestamp, also called epoch time, is simply the number of seconds since January 1, 1970 at midnight UTC. That starting point is the Unix epoch. To store a moment, a computer counts the seconds that have passed since then and keeps just that one number. To show it to a person, the tool runs the count backward: it works out the years, months, days, hours, minutes, and seconds that fit into that total, then adjusts for your time zone. This converter does both directions, so you can turn a timestamp into a readable date or turn a date back into a timestamp.

Engineers picked this design because a single number in UTC has no time zones to argue about and no ambiguous formats like 03/04 that could mean March or April. Ken Thompson and the early Unix team set the epoch, and nearly every operating system, database, and API now stores time this way under the hood. Logs, tokens, and event records all lean on it.

Seconds, Milliseconds, and Time Zones

Two lengths are common. Classic Unix time counts seconds, which is a 10-digit number today. JavaScript and many APIs count milliseconds, which is 13 digits. This tool checks the length and converts either correctly, so you do not have to guess. If your value looks a thousand times too big or small, you likely mixed up the two units.

The timestamp itself carries no time zone. It is one fixed instant. What changes is how you display it. The same number shows a different wall-clock time in Tokyo than in New York, because each place sits at a different offset from UTC. That is why this converter shows your local time, UTC, and the machine-readable ISO 8601 string side by side. When you store or send time, keep it as a UTC timestamp and only convert to local time when you show it to a person. If you also need a fixed fingerprint of an event record rather than its time, our hash generator can help.

Common Mistakes and Practical Tips

The biggest mistake is confusing seconds with milliseconds. Multiply or divide by 1000 when you move between them, or dates land far in the wrong century. A second trap is the year 2038 problem: systems that store the count in a signed 32-bit number run out of room on January 19, 2038, and the value can wrap into a negative date. Modern systems use 64-bit values, which push the limit hundreds of billions of years out, so this only affects old code.

• Store time as a UTC timestamp, convert to local only for display. This avoids off-by-one-day bugs.
• Remember that a timestamp does not know about leap seconds. It treats every day as exactly 86,400 seconds.
• Click Now to grab the current epoch instantly, which is handy for testing logs and cache expiry.
• Decoding a token that holds an exp or iat timestamp? Our Base64 tool helps read encoded parts, and you can drop the time value here to see the real date.

People Also Ask

What is a Unix timestamp in plain terms?

It is the number of seconds counted since midnight UTC on January 1, 1970. That single number is an easy, unambiguous way for computers to record an exact moment in time.

How do I know if my timestamp is in seconds or milliseconds?

Count the digits. A 10-digit value is seconds; a 13-digit value is milliseconds. This converter detects the length and handles either one for you.

Why does the converted local time differ from UTC?

The timestamp has no time zone, so it is the same instant everywhere. Your local clock differs from UTC by your region's offset, which shifts the displayed hours and sometimes the date.

What is the year 2038 problem?

Systems that store Unix time in a signed 32-bit integer overflow on January 19, 2038, at 03:14:07 UTC. After that the number cannot grow, so those systems must move to 64-bit time to keep working.

Can a Unix timestamp be negative?

Yes. Any moment before the 1970 epoch is stored as a negative number. For example, a date in 1969 has a small negative timestamp.

What is ISO 8601 and how is it different from epoch time?

ISO 8601 is a readable date-time text like 2026-07-05T14:30:00Z, while epoch time is a plain number of seconds. ISO is easy for people to read; epoch is easy for machines to store and compare.

How do I convert a date back to a Unix timestamp?

Pick a date and time in the tool above and it shows the matching timestamp in seconds. This is the reverse of turning a number into a date.