On 2017-01-30 13:06, Tony Finch wrote:
It's tricky. Bulletin C is pretty clear about when it thinks TAI-UTC
changes:
from 2015 July 1, 0h UTC, to 2017 January 1 0h UTC : UTC-TAI = - 36s
from 2017 January 1, 0h UTC, until further notice : UTC-TAI = - 37s
Pretty clear? Let's try. What does Bulletin C52 say about the
relationship between UTC and TAI when TAI is equal to
2017-01-01T00:00:36.5. Obviously, UTC - TAI at that instant
must be either -36 s or -37 s.
• If it is -36 s, then UTC = TAI + (UTC - TAI) =
2017-01-01T00:00:36.5 - 36 s
= 2017-01-01T00:00:00.5. This is > 2017-01-01, so by Bulletin C52,
UTC - TAI = -37 s, contradiction.
• If it is -37 s, then UTC = TAI + (UTC - TAI) =
2017-01-01T00:00:36.5 - 37 s
= 2016-12-31T23:59:59.5. This is < 2017-01-01, so by Bulletin C52,
UTC - TAI = -36 s, contradiction.
Fact is, the statement of Bulletin C52 cannot be true when the value of
TAI is during a positive leap second, but it doesn't say so.
So yes, pretty tricky.
Michael Deckers.
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