[LEAPSECS] multiple UTCs

[Zefram]

Tom Van Baak wrote:

>Anyone specifically using such a "tracking" version of UTC

>wants to track earth angle, rather than coordinate with civil

>time, so why not just let them use UT1?


Because access to UT1 requires frequent network access.  I'm thinking
about atomic clocks that sit on a shelf for years, or which will be used
in isolated locations.  We've discussed the use cases (for longer lead
time on leap seconds) in previous threads.


>What these users want is a get_ut1_timeofday(),


This certainly ought to be available too.  It's on my Perl module
todo list.

Even here there are multiple tradeoffs available, when realising UT1 by
atomic clock plus predicted offset.  If you retrieve Bulletin A weekly
then you get a tracking precision on the order of 1 ms.  It looks like
if you examined the daily data, making much shorter-range projections,
you could get a tracking precision more like 100 us.  How network-reliant
are you willing to be, and how close to UT1 do you need to be?

-zefram