Re: [LEAPSECS]Comparing Time Scales

From: Warner Losh <imp_at_BSDIMP.COM>
Date: Fri, 03 Feb 2006 16:47:35 -0700 (MST)

From: James Maynard <james.h.maynard_at_usa.net>
Subject: Re: [LEAPSECS]Comparing Time Scales
Date: Fri, 03 Feb 2006 15:37:40 -0800

> Thanks, guys, for your feedback. Here's another iteration.
>
> The numbering of NTP seconds in the vicinity of a leap second seems to
> differ from one document to another. Here I follow the NTP (version 3)
> specification, RFC 1305, in which the Leap Indicator (sys.leap,
> peer.leap, pkt.leap) is 01 if a positive leap second is to occur at the
> end of the current UTC day, and 00 if no leap second is pending.
>
> UTC = 2005-12-31 23:59:59, NTP seconds = 3 345 062 399, LS_pending = 01
> UTC = 2005-12-31 23:59:60, NTP seconds = 3 345 062 400, LS_pending = 01
> UTC = 2006-01-01 00:00:00, NTP seconds = 3 345 062 400, LS_pending = 00

If you read different documents carefully, you'll see this sequence:

 UTC = 2005-12-31 23:59:60.0, NTP seconds = 3 345 062 400.0, LS_pending = 01
 UTC = 2005-12-31 23:59:60.5, NTP seconds = 3 345 062 399.5, LS_pending = 01
 UTC = 2006-01-01 00:00:00.0, NTP seconds = 3 345 062 400.0, LS_pending = 00

Where the 399 second repeats. The documents say that just after time
is incremented to 400, the last second of the day is repeated....

Warner
Received on Fri Feb 03 2006 - 15:49:01 PST