UTC Time Zone Explained and Unix Epoch Timestamp
The Unix timestamp tracks time as the total number of seconds since January 1, 1970, UTC. UTC is Coordinated Universal Time, not actually a time zone. It is a "time standard". This time standard is crucial since we need a universal time across all systems worldwide. A Unix timestamp is just an integer, which means there's no room for time zones in its data.
Hence, it stays in UTC. Unlike UTC, GMT is a time zone. GMT can change with seasons due to daylight saving time. GMT changes to British Summer Time in the summer, and UTC does not change.
Another point to know is the Unix timestamp issue on January 19, 2038. 32-bit systems will fail to represent time past this date, but 64-bit systems solve this.
Unix timestamp format can represent time in seconds, milliseconds, microseconds, and nanoseconds for higher precision. For example, PubNub's API returns timestamps at the nanosecond level.
