[EMAIL PROTECTED] schreef: > http://hpiers.obspm.fr/eop-pc/earthor/utc/leapsecond. > html > > "... Since the system was introduced in 1972, " > > The table starts in 1972. Before that, GMT was > in use - not UT1!
Not true. UT1 existed at least since 1958. In that year, TAI (atomic time) was synchronized with UT1. UT1 is based on the observed length of the day (corrected for some large scale effects like the movement of the poles). As it is observation based, it is not a good timescale to base civil time on. UT was used for that. Periodically the correspondence of UT and UT1 was checked, and UT was corrected by changing the length of the day, and by adding a small time adjustment to account for the accumulated difference. Civil time was based on UT: GMT was UT+0000, MET was UT+0100, EST was UT-0500 IIRC (as long as you're not in Australia). So the role of UT/GMT was taken over by UTC, not by UT1. Eugene
