John Cowan said:
A count of UTC seconds since the Epoch is the same as a count of TAI seconds Only if you are talking about broken-down labels for time. But I was talking about time expressed as a count of seconds. For example, the two adjacent real-time seconds with broken-down labels 1998-12-31 23:59:60 and 1999-01-01 00:00:00 UTC have the same count-of-seconds since the epoch. No, I don't believe so. The two adjacent seconds you mention have the same _Posix_ time, but the number of elapsed UTC seconds = TAI seconds = SI seconds since the Epoch is not the same;
On the other hand, Paul is right to talk about UTC-TAI changing. Perhaps a way to think about it is that UTC has two kinds of seconds: normal and leap. number of TAI seconds = number of UTC normal seconds + leap seconds number of POSIX seconds = number of UTC normal seconds TAI broken down time is based on number of TAI seconds POSIX broken down time is based on number of POSIX seconds UTC broken down time is based on number of UTC normal seconds It's not really useful to talk about the number of UTC seconds elapsed, since the whole point of UTC is its broken-down form. The only useful thing is the number of normal seconds elapsed. So I suppose I'm with Paul, here. -- Clive D.W. Feather | Work: <clive@demon.net> | Tel: +44 20 8495 6138 Internet Expert | Home: <clive@davros.org> | Fax: +44 870 051 9937 Demon Internet | WWW: http://www.davros.org | Mobile: +44 7973 377646 Thus plc | |