Analog clocks and leap seconds

From: Tom Van Baak <>
Date: Fri, 13 Jan 2006 07:31:50 -0800

Michael Sokolov writes:
> I cannot make the beautiful analog clock on the tower show 23:59:60.
> But it's trivial to make it occasionally take 1.1 SI seconds instead of
> 1 SI second to turn its hands by 1 civil second.

Yes, this is one of the awkward features of a leap
second (positive leap second, at least). In practice
few clocks with analog displays are accurate enough
to even worry about leap seconds.

But if you were to design an analog clock that was
somehow leap second compatible here is my list
of possible implementations:

- You can have it run UT1 instead of UTC.

- For extra credit, you can have it run sidereal.

- You can pause at :59 or :00 for a second. Or pause
  halfway in between.

- You can slow down a bit sometime before the leap
  second and resume normal speed sometime after
  the leap second such that one second is wasted.
  Even 5 or 15 seconds before and after would be
  sufficient that no one would notice the rate change.

- You can slow it down to exactly 1/2 speed between
  :59 and :00. This, in my opinion, would be the most
  visually pleasing. As of last week, photos of digital
  23:59:60 displays are now common. But an analog
  hand slowing down half speed between 59 and 00
  would be quite unique. Similarly use 2x speed for a
  negative leap second, should one to ever occur.

- You could wait for the second hand to hit :00 and
  then go backwards for 1/2 second, then forwards
  for 1/2 second. Kind of weird, but it would work.

- You can design it with 61 seconds around the circle
  and jump over number 60 (go from 59 to 00) every
  minute except for when a positive leap second occurs.
  Also kind of weird, but the further into the future the
  more it would be appreciated.

Received on Fri Jan 13 2006 - 07:38:30 PST

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