Hi Mouse, On Mon, 2008-10-27 at 13:55 -0400, der Mouse wrote: > > So if leap seconds are arbitraliy added by scientist how does the > > Linux date command know when one is added. > > (I assume that's a question, despite the non-question punctuation.) It > knows more or less the same way any modern Unix variant's date command > does - by using the UTC<->localtime conversion rules on hand. > > > Is that something that's part of the timezone file? > > Basically, yes. (I assume UTC<->localtime conversion code not driven > off files exists, but it either must have some analog or must ignore > leap seconds.) > > Yes, this means you need to update your timezone data every time a leap > second is added, if you care about leap seconds. (Or just every six > months or so if you don't want to have to follow leap-second news; I > think leap seconds are introduced only on six-month boundaries.)
No. UTC<-> Localtime is not affected by leapseconds. GPS time <-> UTC is the relationship that is affected. Your typical (unix) computer will always run its local clock in UTC. An stratum 1 NTP-server usually gets its time from a GPS receiver. It is the responsibility of the refclock_driver and NTP to insert the leapsecond in a "good" way. It is not obvious that "good" is the same as stepping the time one second at the epoch. You might want to make a "smooth" transition by adjusting the frequency over some time instead. This will give your clock a more continous time, which might be preferable. This is especially true if we were ever to loose a second in a leapsecond event. As long as you have an upstream internet connection to a good NTP server you should be ok. If you have an isolated network with your own UTC sync solution you should take more care. -- Björn _______________________________________________ timekeepers mailing list [email protected] https://fortytwo.ch/mailman/cgi-bin/listinfo/timekeepers
