Epoch
Sometimes referred to as Unix time, epoch is the operating system starting point that determines the computers current time and date by counting the number of ticks that have elapsed since the epoch date. Below is a listing of different operating systems and their associated tick and epoch.
| Operating System | Tick | Epoch |
|---|---|---|
| Apple Mac OS | 1 sec | January 1, 1904 to February 6, 2040 |
| Microsoft DOS | 1 sec | January 1, 1980 to January 1, 2108 |
| Microsoft Windows | 100 ns | January 1, 1601 to AD 30828 |
| OpenVMS | 100 ns | November 17, 1858 to AD 31086 |
| POSIX | 1 sec | January 1, 1970 to January 19, 2038 |
| S/390 | 244.14 picosec | January 1, 1970 to January 19, 2038 |
| Unix | 1 sec | January 1, 1970 to January 19, 2038 |
When trying to figure out the difference between two epoch values when programming you can use the below values to help determine how many hours, seconds, days difference there is by subtracting the two epoch values and then dividing by one below values. For example, if the difference between the two was 14,400, dividing that by 3600 shows the difference is 4 hours.
| Time period | Epoch second equivalent |
|---|---|
| 1 minute | 60 |
| 1 hour | 3600 |
| 1 day | 86400 |
| 1 week | 604800 |
| 2 weeks | 1209600 |
| 3 weeks | 1814400 |
| 1 month | 2419200 |
| 6 months | 14515200 |
| 1 year | 29030400 |
| 1 decade | 290304000 |
Also see: Measurement, Operating system definitions, Programming definitions, Tick, Time