What is Unix Timestamp?
Unix Timestamp (also known as Unix Epoch Time or POSIX time) is a system for tracking time as a running total of seconds since the Unix Epoch - January 1, 1970, 00:00:00 UTC. It provides a simple, timezone-independent way to represent a specific moment in time.
Quick Facts
| Full Name | Unix Epoch Time |
|---|---|
| Created | 1970 (with Unix operating system) |
| Specification | Official Specification |
How It Works
The Unix timestamp was introduced with the Unix operating system in the early 1970s. It represents time as a single integer, making it easy to store, compare, and calculate time differences. Traditional Unix timestamps use a signed 32-bit integer, which will overflow on January 19, 2038 (the Y2K38 problem). Modern systems use 64-bit integers to extend this range. Millisecond and microsecond precision variants multiply the base timestamp by 1000 or 1000000 respectively.
Key Characteristics
- Counts seconds since January 1, 1970, 00:00:00 UTC
- Timezone-independent representation of time
- Simple integer format easy to store and compare
- 32-bit systems face Y2K38 overflow problem
- Millisecond precision uses 13-digit timestamps
- Negative values represent dates before 1970
Common Use Cases
- Database timestamp storage
- API request/response timestamps
- Log file timestamps
- Calculating time differences and durations
- Cross-timezone time synchronization
Example
Loading code...Frequently Asked Questions
What is the Unix Epoch and why is January 1, 1970 used?
The Unix Epoch is the reference point for Unix timestamps - January 1, 1970, 00:00:00 UTC. This date was chosen when Unix was being developed at Bell Labs in the early 1970s. It was a convenient recent date at the time that would minimize storage requirements while covering the foreseeable future. The 32-bit signed integer format could represent dates from 1901 to 2038.
How do I convert a Unix timestamp to a human-readable date?
In JavaScript: new Date(timestamp * 1000) for seconds, or new Date(timestamp) for milliseconds. In Python: datetime.fromtimestamp(timestamp). In PHP: date('Y-m-d H:i:s', timestamp). Most programming languages have built-in functions for this conversion. Remember that Unix timestamps are in UTC, so you may need to adjust for local timezone.
What is the Y2K38 problem and how does it affect Unix timestamps?
The Y2K38 problem (Year 2038 problem) occurs because traditional 32-bit signed Unix timestamps will overflow on January 19, 2038, at 03:14:07 UTC. After this moment, the timestamp would wrap to a negative number representing December 1901. Modern systems use 64-bit integers which extend the range to billions of years. Most current software and databases have already transitioned to 64-bit timestamps.
Should I use seconds or milliseconds for Unix timestamps?
Traditional Unix timestamps use seconds (10 digits), but JavaScript and many modern APIs use milliseconds (13 digits). Choose based on your needs: seconds are sufficient for most applications like logging and scheduling. Milliseconds provide finer granularity for performance measurement or when sub-second precision matters. Always document which format your system uses to avoid confusion.
How do I get the current Unix timestamp?
In JavaScript: Math.floor(Date.now() / 1000) for seconds or Date.now() for milliseconds. In Python: import time; int(time.time()). In PHP: time(). In Bash: date +%s. In SQL (MySQL): UNIX_TIMESTAMP(). All these return the current UTC time as a Unix timestamp, regardless of the local timezone setting.