> > > The system clock needs to be UTC, not UTC =C2=B1 some offset stuck > > > somewhere that keeps some form of running tally of the current leap > > > second offset since the epoch. > > > Nope. UTC *includes* leap seconds already. It's UT1 that does not. > > > Are you suggesting that NTP timekeeping should be based on UT1? > > The system clock should be based on UT1 and should be monotonically increas= > ing since this matches the common concept of time. Calculations done with = > this value are all based on it being UT1 and using the "common" notion of U= > T1 rules. The root cause of the difficulties is that someone decided that = > the system clock would not maintain "wall clock" time (UT1) but rather some= > other timebase and then "step" that time to keep it in sync with UT1. > > NTP can keep time in UTC (or anything else) if it wants, but it should disc= > ipline the system clock to monotonically increasing UT1.
UTC is the universal time. UT1 is "astronomical time". As the definition of a atomic second is 9192631770 complete oscillations of cesium 133 between enery level 3 and 4, "everyone" can make a second in their lab, that's TAI. Just add the lepsecond ofset and you have UTC. UT1-UTC is done by observations from radio astronomers VLBI telecopes and a comitee, you can't make one in your lab, and it's not real time. --P (The only SI metric you can't make is a kilogram, you have to have one of the 28 kilos in the world..)