On Fri 2007-01-12T18:35:55 +0000, Tony Finch hath writ:
> According to the slides linked from Dave Mills's "Timekeeping in the
> Interplanetary Internet" page, they are planning to sync Mars time to UTC.
> http://www.eecis.udel.edu/~mills/ipin.html

Neverminding the variations on Mars with its rather more eccentric
orbit, the deviations from uniformity of rate of time on earth alone
create an annual variation of almost 2 ms between TT and TDB.  This is
also ignoring variations in time signal propagation through the solar
wind when Mars is near superior conjunction.

To some applications 2 ms in a year is nothing.  From an engineering
standpoint a variation of 2 ms in a year on Mars is certainly better
than any time scale that could be established there in lieu of landing
a cesium chronometer.  To other applications 2 ms in a year may be
intolerably large.

So the question remains: At what level do distributed systems need
access to a time scale which is uniform in their reference frame?
And my question: Can something as naive as POSIX time_t really serve
all such applications, even the ones on earth, for the next 600 years?

Steve Allen                 <[EMAIL PROTECTED]>                WGS-84 (GPS)
UCO/Lick Observatory        Natural Sciences II, Room 165    Lat  +36.99858
University of California    Voice: +1 831 459 3046           Lng -122.06014
Santa Cruz, CA 95064        http://www.ucolick.org/~sla/     Hgt +250 m

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