Time Standard

see unix time

resource international atomic time "TAI" (based on atomic clocks) versus universal time "UT1" (based on Earth's rotation) versus coordinated universal time (an integer number of leap seconds offset from TAI to remain in sync with UT1) --- leap-seconds.list --- https://data.iana.org/time-zones/data/leap-seconds.list

TAI is a high-precision time standard based on the passage of proper time on Earth. it is a weighted average of the time kept by numerous atomic clocks worldwide, the majority of which are caesium clocks; the international system of units definition of the second is based on caesium