Comment by sq_

I find this stuff really interesting, so if anyone's curious, here's a few more tidbits:

GPS system time is currently 18s ahead of UTC since it doesn't take UTC's leap seconds into account [0]

This (old) paper from USNO [1] goes into more detail about how GPS time is related to USNO's realization of UTC, as well as talking a bit about how TAI is determined (in hindsight! - by collecting data from clocks around the world and then processing it).

[0] https://www.cnmoc.usff.navy.mil/Our-Commands/United-States-N... [1] https://ntrs.nasa.gov/api/citations/19960042620/downloads/19...