nanog mailing list archives
RE: Leap Second planned for 2016
From: "Keith Medcalf" <kmedcalf () dessus com>
Date: Sat, 09 Jul 2016 15:37:36 -0600
POSIX (Unix) (normal) time does not have leap seconds. Every POSIX (Unix) (normal) minute has exactly 60 seconds. Every POSIX (Unix) (normal) hour has exactly 60 minutes. Every POSIX (Unix) (normal) day has exactly 24 hours. Every POSIX (Unix) (normal) year has 365 days, unless it is a leap year, in which case it has exactly 366 days. The POSIX time is the number of seconds (or parts thereof) that has passed since midnight, 1 January 1970 GMT. The time scale is UT1. Outside of very specialized scientific applications, EVERY computer system everywhere uses POSIX time and does time/date calculations based on POSIX time (UT1). UTC time has leap seconds. This is because UTC is a "different" time-scale than the UT1 timescale on which POSIX/Unix time is based. UTC proceeds at a different "rate" from UT1 and so, from time to time, UTC time must be adjusted to keep it in sync with POSIX/Unix (normal) time.
-----Original Message----- From: NANOG [mailto:nanog-bounces () nanog org] On Behalf Of Valdis.Kletnieks () vt edu Sent: Saturday, 9 July, 2016 15:12 To: Saku Ytti Cc: NANOG list Subject: Re: Leap Second planned for 2016 On Sat, 09 Jul 2016 12:14:03 +0300, Saku Ytti said:Check the implementation on your PC. This is why code is broken and people don't even know it's broken. You have to use monotonic time to measure passage of time, which is not particularly easy to do portable, in some languages.It doesn't help that the POSIX standard doesn't represent leap seconds anyplace, so any elapsed time calculation that crosses a leap second is guaranteed to be wrong....
Current thread:
- Re: Leap Second planned for 2016, (continued)
- Re: Leap Second planned for 2016 Saku Ytti (Jul 08)
- Re: Leap Second planned for 2016 Harlan Stenn (Jul 08)
- Re: Leap Second planned for 2016 Patrick W. Gilmore (Jul 08)
- Re: Leap Second planned for 2016 Chris Adams (Jul 08)
- Re: Leap Second planned for 2016 Eric S. Raymond (Jul 09)
- Re: Leap Second planned for 2016 A . L . M . Buxey (Jul 09)
- Re: Leap Second planned for 2016 Saku Ytti (Jul 09)
- Falsehoods programmers believe about time, etc (was Re: Leap Second planned for 2016) Jay R. Ashworth (Jul 10)
- Re: Leap Second planned for 2016 Saku Ytti (Jul 09)
- Re: Leap Second planned for 2016 Valdis . Kletnieks (Jul 09)
- RE: Leap Second planned for 2016 Keith Medcalf (Jul 09)
- Re: Leap Second planned for 2016 Saku Ytti (Jul 10)
- Re: Leap Second planned for 2016 Steve Allen (Jul 10)
- Re: Leap Second planned for 2016 Mikael Abrahamsson (Jul 10)
- Re: Leap Second planned for 2016 Jimmy Hess (Jul 10)