What is the Unix timestamp?
Unix Timestamp is a system for expressing time in seconds since 1st January 1970 00:00:00 UTC. It is a standard used by Unix computers to identify the order and date of events, such as file creation and modification dates, access times, login times, and logout times.
It is widely used in Unix systems because it has better performance than alternative time representations such as milliseconds or microseconds. The Unix timestamp was invented by Ken Thompson and Dennis Ritchie in the 1960s and 1970s.
In summary, the Unix timestamp is a way to track time as a running total
of seconds. This count starts at the Unix Epoch on January 1st, 1970 at
Universal Time). Therefore the Unix time stamp is merely the number
of seconds between a particular date and the Unix Epoch. It should also be
pointed out that no matter where you are located on the globe the Unix
time is always stored in UTC standard format (note that sometimes "GMT"
(Greenwich Mean Time) is used, which is technically same like UTC but it
is already outdated).
What happens on January 19, 2038?
On this date the Unix timestamp will cease to work due to a 32-bit overflow because the timestamp is stored as a signed 32-bit number. Before this moment all active programs will need to adopt a new convention for timestamps, maybe by switching to unsigned 32-bit or directly to 64-bit.