Re: [LEAPSECS] The real problem with leap seconds
Mark Calabretta wrote:
> You're still not getting the point that UTC is just a representation
> of TAI.
OK, let me try again.
UTC (since 1972) is a disseminated timescale that is equal to TAI
except for additional date and time codes transmitted with the
signal. These codes indicate the values of TAI - DTAI for each
full minute of TAI - DTAI.
In a reading of UTC, (the most recent values of) these date and
time codes can be taken as is so as to yield a reading that
approximates UT1. The codes may also be used to derive the value of
DTAI (from a table of leap seconds since 1972), and thus, to yield
a reading of TAI. When a timestamp is characterised as UTC
(rather than TAI), then the first type of reading is implied.
In order to ensure a unique derivation of TAI from a recorded
reading of UTC in the vicinity of a positive leap second (where
DTAI jumps up by 1 s and the value of TAI for a given value of
TAI - DTAI is not unique), the UTC reading that corresponds to the
earlier TAI value shall be recorded with a second field >= 60 s,
and the other UTC reading, with a second field < 60 s.
Michael Deckers (still trying to understand the topology you referred to)
Received on Mon Jan 16 2006 - 04:11:23 PST
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: Sat Sep 04 2010 - 09:44:55 PDT