The leap seconds are coming, the leap seconds are coming

The leap seconds are coming, the leap seconds are coming.

Oh, great–first the government mucks with DST, and now leap seconds are back for the first time in 7 years. I was starting to think that we were done with them for good.

My timezone is going to have an extra second added at 3:59:60 PM on
December 31st, 2005. Fun; I wonder how many of the devices that I deal
with will do the right thing with the extra second. Odds are most of
them will just end up an extra second off. I assume that NTP
has a way of dealing with this, although it might just be outside of
the protocol’s scope–leap seconds really just change the
seconds-since-some-epoch to human-visible-date mapping. (Update: it’s complicated)

Since leap seconds aren’t new, and I don’t really care about
sub-second timing precision on any of my devices, I doubt I’ll even
notice the change, although undoubtedly there are devices on the market
that will have problems; I wouldn’t be surprised if there’s a cheap GPS
receiver somewhere with leap seconds issues.

This reminds me of two of the pedantic sysadmin interview questions
that I’ve never really had the guts to ask a real candidate–“exactly
how many hours are in a day?” and “how many seconds are there in a
minute?” Strictly speaking, the answers are “23, 24, or 25, depending
on DST transitions” and “59, 60, or 61, depending on leap seconds.” The
23/24/25 thing actually bites new sysadmins–never schedule something
that needs to happen exactly once per week to happen between 2:00 and
3:00 local time on a Sunday morning, because once per year it won’t
happen at all, and another time it’ll happen twice.  [*scottstuff*]

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