turning clocks back

Markus Kuhn Markus.Kuhn at cl.cam.ac.uk
Sun Oct 11 10:44:59 UTC 1998

Paul Eggert wrote on 1998-10-11 00:25 UTC:
>    Adjusting clocks backwards is just a figure of speech to explain
>    DST switches to the general population without introducing proper
>    notation.
> Sorry, you've lost me.  Adjusting clocks backwards is a figure of
> speech?  In a couple of weeks, I'll be wandering over my house,
> office, and car manually adjusting dozens of dumb localtime clocks
> backward.  On that day it certainly won't feel like a figure of
> speech.  :-)

I think it is time mankind should advance the state of the art on
household clocks a bit: Instead of wandering around to turn them back,
you should be able to program them such that tonight they will go
through the hours 1, 2A, 2B, 3, etc. Then DST switching becomes an
exercise of inserting and deleting leap hours into the time scale,
removing the ambiguity of the repeated hour. Most clocks have integrated
circuits, therefore this functionality would cost practically nothing to
add. If you know a clock manufacturer desperately looking for new
features to add, feel free to forward this patent-free idea.
Unfortunately, the only self-adjusting clocks that I know of are
computers and radio clocks.

Actually thinking about it, there is a neat way of encoding hour 2A in a
distinguishable way even on "analog" clock displays: Just stop the
motion of the hour pointer for 60 min during hour 2A, and it will be
immediately recognizable whether you are in hour 2A or 2B (except
perhaps for the first few minutes of the hour, where the smaller pointer
hasn't moved yet much during hour 2B).


Markus G. Kuhn, Security Group, Computer Lab, Cambridge University, UK
email: mkuhn at acm.org,  home page: <http://www.cl.cam.ac.uk/~mgk25/>

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