What is Epoch Time?
Epoch time refers to the reference point (January 1, 1970, 00:00:00 UTC) from which Unix timestamps are calculated. The term 'epoch' specifically denotes this moment in time that serves as the origin for Unix time systems.
Quick Facts
| Full Name | Unix Epoch Time |
|---|---|
| Created | 1970 (Unix operating system) |
| Specification | Official Specification |
How It Works
The Unix Epoch (January 1, 1970, 00:00:00 UTC) was chosen as the reference point for Unix time when the operating system was being developed at Bell Labs. While 'epoch time' and 'Unix timestamp' are often used interchangeably, technically the epoch refers to the starting point, while the timestamp is the count of seconds since that point. Different systems may use different epochs - for example, Windows uses January 1, 1601, macOS Classic used January 1, 1904, and Excel uses January 1, 1900. The Unix Epoch has become the de facto standard for most modern computing systems, web APIs, and databases. Understanding the distinction between the epoch (reference point) and timestamp (elapsed time) is important when working with systems that use different epoch origins.
Key Characteristics
- Unix Epoch: January 1, 1970, 00:00:00 UTC - the most widely used epoch
- Windows Epoch: January 1, 1601 - used in Windows file times (FILETIME)
- macOS Classic Epoch: January 1, 1904 - used in older Mac systems
- Excel Epoch: January 1, 1900 - used in spreadsheet applications
- NTP Epoch: January 1, 1900 - used in Network Time Protocol
- GPS Epoch: January 6, 1980 - used in GPS systems
Common Use Cases
- Converting timestamps between systems with different epochs
- Understanding legacy system time representations
- Cross-platform time synchronization and conversion
- Debugging time-related issues in multi-system environments
- Historical data migration between different epoch-based systems
Example
Loading code...Frequently Asked Questions
Why was January 1, 1970 chosen as the Unix epoch?
January 1, 1970 was chosen as a convenient, round date when Unix was being developed at Bell Labs. It was recent enough to be useful for contemporary timestamps while far enough in the past to represent most relevant dates.
What is the Year 2038 problem (Y2K38)?
The Y2038 problem occurs because 32-bit signed integers storing Unix timestamps will overflow on January 19, 2038 at 03:14:07 UTC. Systems using 32-bit time will wrap to negative values, representing dates in 1901. Modern systems use 64-bit integers to avoid this.
What is the difference between epoch time in seconds and milliseconds?
Epoch time in seconds is a 10-digit number (e.g., 1704067200), while milliseconds is 13 digits (e.g., 1704067200000). Milliseconds provide more precision for timing events. JavaScript's Date.now() returns milliseconds.
How do I convert epoch time to a human-readable date?
In JavaScript: new Date(epochSeconds * 1000).toISOString(). In Python: datetime.fromtimestamp(epoch_seconds). In Bash: date -d @epoch_seconds. Remember to multiply by 1000 if working with seconds in JavaScript.
Can epoch time represent dates before 1970?
Yes, dates before January 1, 1970 are represented as negative epoch values. For example, December 31, 1969 at 23:59:59 UTC is -1 in epoch seconds. This allows representing historical dates back to December 1901 in 32-bit systems.