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 at 00:00:00 UTC — a reference point known as the Unix Epoch. It is a simple, unambiguous, and timezone-independent way to represent any moment in time. Almost every programming language, operating system, and API uses Unix timestamps internally.
For example, the timestamp 1741478400 means "1,741,478,400 seconds have passed since the Unix Epoch", which corresponds to March 9, 2025 at 08:00:00 UTC regardless of where you are in the world.
Seconds vs. milliseconds
There are two common variants:
- Seconds (10 digits): The traditional Unix format, used by most operating systems, databases, and POSIX APIs. Example:
1741478400.
- Milliseconds (13 digits): Used by JavaScript's
Date.now(), Java's System.currentTimeMillis(), and many web APIs. Example: 1741478400000.
This converter auto-detects which format you're using based on the number of digits.
How to get the current timestamp in code
| Language |
Seconds |
Milliseconds |
| JavaScript | Math.floor(Date.now()/1000) | Date.now() |
| Python | int(time.time()) | int(time.time()*1000) |
| PHP | time() | round(microtime(true)*1000) |
| Java | Instant.now().getEpochSecond() | System.currentTimeMillis() |
| Go | time.Now().Unix() | time.Now().UnixMilli() |
| SQL | UNIX_TIMESTAMP() | — |
Frequently asked questions
Does a Unix timestamp depend on the timezone?
No. A Unix timestamp always represents a fixed point in UTC. Timezones only affect how the timestamp is displayed as a human-readable date. The underlying number is always the same anywhere in the world.
What is the Year 2038 problem?
On 32-bit systems, the maximum Unix timestamp is 2147483647 (231−1), which corresponds to January 19, 2038 at 03:14:07 UTC. After that, a 32-bit counter overflows to a negative number. Modern 64-bit systems are unaffected as they support timestamps well beyond year 292 billion.
How do I convert a date to a Unix timestamp in JavaScript?
Use new Date('2025-03-09T08:00:00Z').getTime() for milliseconds, or divide by 1000 for seconds. Always include the Z suffix to specify UTC and avoid local timezone ambiguity.
What is ISO 8601?
ISO 8601 is an international date format standard. Example: 2025-03-09T08:00:00.000Z. The trailing Z means UTC. It is the format returned by JavaScript's Date.prototype.toISOString() and widely used in APIs and databases.