GPS, UTC and TAI Clocks (2001) | Hacker News Reader

GPS, UTC and TAI Clocks (2001)

leapsecond.com

46 pointsturrini9 comments

The UTC time scale which currently serves as the basis for all civil time is defined to be calculated from UT1. If civilization continues to desire the use of mean solar time then UT1 will eventually fail to serve that need.

Within the next millennium the IAU will have to consider defining and naming a new version of UT to serve as the quantity which is measured by analemmatic sundials. A name for that time scale might perhaps be Analemmatic Universal Time (UTA).

ok. We better form a committee. We don't have much time.

A committee whose purpose is to give us one more time!

Fortunately, almost two decades later a committee decided to break the connection between UTC and UT1 and stop having leapseconds some time before 2035.

GPS does not account for leap seconds (2002) - https://news.ycombinator.com/item?id=33620933 - Nov 2022 (53 comments)

Would you mind recapitalizing Tai to TAI?

Done. Thanks!

I'd not heard of TAI before, the page doesn't explain how it differs from Loran-C, though perhaps some of the reference links will. I'll have to check them out.

TAI, UTC, and GPS and LORAN-C time are all the same time scale but at offsets resulting from having stopped adopting leap seconds at different points. The only confusing thing is that we tend to talk about TAI's variation from UTC rather than the variation of each system from TAI, which is fixed for everything but UTC (until 2035). We can thus sort of discuss them like time zones:

    UTC: TAI-37s
    GPS: TAI-19s
    LORAN-C: TAI-10s

UTC will stop applying leap seconds but hasn't yet, so the offset for UTC could potentially change. Once UTC stops applying leap seconds, they will all be fixed and these offsets will just be technical details. Of course the whole thing has actually become obsolete in the case of LORAN-C which was shut down, but it seems less likely that TAI will fall out of use.

Different offsets. That's about it; they both tick at the same rate and ignore leap seconds.

The mention of LORAN-C kind of dates the page, actually. The last remaining LORAN transmitters were shut down at the end of 2015.

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