The operating system starting time that is used as a beginning point to determine the computers current time and date by counting the number of ticks that have elapsed since the epoch. 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 would show 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 |
- If your computer is getting set back to the starting Epoch time or you're loosing time see document CH000386 for additional information about this issue.
Also see: Measurement, Operating system definitions, Programming definitions, Tick, Time | |
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