nanog mailing list archives
Re: REMINDER: Leap Second
From: Valdis.Kletnieks () vt edu
Date: Sun, 25 Jan 2015 13:15:27 -0500
On 25 Jan 2015 17:29:25 +0000, "John Levine" said:
It shares with time zones the problem that you cannot tell what the UNIX timestamp will be for a particular future time. If you want to have something happen at, say, July 2 2025 at 12:00 UTC you can guess what the timstamp for that will be, but if there's another leapsecond or two, you'll be wrong.
It shares another problem - that doing calculations across a boundary is difficult. If you have a recurring timer that pops at 23:58:30 on June 30, and you want another one in 2 minutes. do you want a timer that the next pop is at 00:00:30 - or 00:00:29? The operating system can't tell whether the desired semantic is "as close to every 120 elapsed seconds as possible" or "as close to the half-minute tick as possible". And of course doing interval math across several years where you cross multiple leap seconds is even more problematic - for some corner cases that have an endppoint nearmidnight, doing a naive "timestamp in seconds +/- 86400 * number of days" can land you on the wrong *day*, with possibly serious consequences...
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Current thread:
- REMINDER: Leap Second Jay Ashworth (Jan 25)
- Re: REMINDER: Leap Second Mike. (Jan 25)
- Re: REMINDER: Leap Second Karsten Elfenbein (Jan 25)
- Re: REMINDER: Leap Second Ken Chase (Jan 25)
- Re: REMINDER: Leap Second Joe Klein (Jan 25)
- Re: REMINDER: Leap Second Karsten Elfenbein (Jan 25)
- Re: REMINDER: Leap Second John Levine (Jan 25)
- Re: REMINDER: Leap Second Valdis . Kletnieks (Jan 25)
- Re: REMINDER: Leap Second Ken Chase (Jan 25)
- Re: REMINDER: Leap Second Stephen Satchell (Jan 25)
- Re: REMINDER: Leap Second Barney Wolff (Jan 25)
- Re: REMINDER: Leap Second TR Shaw (Jan 25)
- Re: REMINDER: Leap Second Barney Wolff (Jan 26)
- Re: REMINDER: Leap Second John Levine (Jan 26)
- Re: REMINDER: Leap Second Barry Shein (Jan 26)
- Re: REMINDER: Leap Second Mike. (Jan 25)