what is unixtime?

Unix time is a simple way to count time.

It is the number of seconds since 1 January 1970 (UTC), ignoring leap seconds.

Computers use it because a number is easy to store, compare, and share.

Unix time also skips the complexity of timezones, so the same number means the same moment everywhere.

Unix time does not count leap seconds. Instead, a positive leap second repeats one Unix timestamp and a negative leap second skips one.

who runs unixtime?

I do, because I use it myself.