TAI

programming

Stands for: International Atomic Time

A continuous atomic timescale with no leap seconds.

International Atomic Time is a uniform timescale kept by atomic clocks that never inserts leap seconds. UTC is derived from TAI but adds leap seconds to stay aligned with the Earth's rotation, so the two drift apart by whole seconds.

International Atomic Time is a continuous count with no leap seconds, which makes it the timescale that behaves correctly for arithmetic. UTC is TAI adjusted by an integer number of leap seconds to stay aligned with the earth's rotation.

That difference is why systems needing monotonic time internally often work in TAI or in a smeared timescale and convert for display. Anything computing a duration across a leap second in UTC can produce a negative or zero interval, which is the failure that has taken real services down. With leap seconds due to be discontinued by the 2030s, the distinction becomes historical, and until then it remains a live consideration for anything doing precise timing.

Also known as: tai

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