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Re: Leap second reminder

  • From: Kevin Day
  • Date: Sat Dec 31 14:34:13 2005

On Dec 31, 2005, at 11:58 AM, Kevin Day wrote:

Just a reminder, at midnight UTC there's a leap second added to most time systems.

I've had quite a few replies already off list, that I'll sum up:

1) ISO 8601 specifically defines ":60" as a valid representation for seconds, just for this event.  If your app breaks, it's probably not obeying the relevant RFC.

2) Anything using the obvious implementation of regular expressions to check for a valid time is probably going to fail "23:59:60", leading to events not being logged,  or transient weirdness for that second.

One example I thought of after a few minutes is SpamAssassin, who will flag a mail header:

Date: Sat, 31 Dec 2005 23:59:60 +0000

As "INVALID_DATE", bumping up its spam score by 1.7 to 2.0(by default), because of the regexp it uses which contains "[0-5][0-9]"

3) Two people have noted that their Juniper routers spat out some strange ntpd messages earlier today, such as:

Dec 31 06:26:46 hostname xntpd[66479]: time reset 0.999681 s
Dec 31 06:48:11 hostname xntpd[66479]: time reset -0.437785 s
(local time set to America/Chicago)

4) You can't set your clock to 23:59:60 manually, which makes testing what's going to happen difficult. 

5) The "leap second pending" bit that's supposed to have been set by now in NTP isn't being set by some clock sources, leading some to wonder what they're planning on doing at midnight.