Time scales and civil time
Unix time
Also: Unix-tijd
Unix time counts the number of seconds elapsed since the Unix epoch: 1 January 1970, 00:00:00 UTC. Almost every operating system and network device stores time internally as this number, independent of time zones and calendars.
Systems that store the counter in 32 bits hit an overflow in 2038 (the 'Year 2038 problem'); 64-bit counters solve this.