Danny Mayer wrote: > Martin Burnicki wrote: >> The article I was referring to can also be found in the NTP questions >> mailing list archive: >> http://lists.ntp.isc.org/pipermail/questions/2005-October/007296.html >> >> In the log output you can see that the tick adjustment value is >> temporarily changed from 156250 to 78125, so the system time temporarily >> increases with half speed only until the time offset introduced by the >> leap second has been compensated. >> > > I hope you mean *decrease* with half speed. You are adding a second not > subtracting it so the clock needs to slow down.
No, there is just some misunderstanding here. What I meant is the following: Assuming the system clock is really close to UTC before the leap second. Both increase at a rate of 1 sec per second, which is "normal speed". If the leap second is inserted into UTC the system clock would normally also increase by 1 second, so after the leap second the system clock would be 1 second ahead of UTC without correction: sys clock UTC ------------ ------------ 23:59:58.000 23:59:58.000 23:59:59.000 23:59:59.000 00:00:00.000 *23:59:60.000 <- leap sec 00:00:01.000 00:00:00.000 <- w/o correction sys clock 1 sec ahead 00:00:02.000 00:00:01.000 00:00:03.000 00:00:02.000 If we start slowing down the system clock at the beginning of the leap second then the system clock "waits" for UTC to catch up: sys clock UTC ------------ ------------ 23:59:58.000 23:59:58.000 23:59:59.000 23:59:59.000 00:00:00.000 *23:59:60.000 <- leap sec, start correction 00:00:00.500 00:00:00.000 <- sys clock gains 0.5 sec/sec only 00:00:01.000 00:00:01.000 <- UTC caught up, correction finished 00:00:02.000 00:00:02.000 00:00:03.000 00:00:03.000 This means the *rate* of the system clock is decreased to half speed for 2 seconds, but the system clock still *increases* with half speed during this interval. Martin -- Martin Burnicki Meinberg Funkuhren Bad Pyrmont Germany _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
