Originally Posted by
Senior Paper Monitor
I still haven't recovered from GMT becoming UCT (I would have felt much better about it if I could have got on the global wandering committee discussing it though)
GMT was fine in an age when clocks weren't too accurate. It was handy to know how many seconds there were going to be in a given calendar year even if no one knew exactly how long each second was because this could only be determined retrospectively via astronomical observation.
Now that we live in the age of very accurate atomic clocks it is more useful to have seconds of a standard length and then add a leap second every now and then to keep UTC within a second of the 'mean time' UT1. UT1 is the modern equivalent of GMT, determined by astronomical observation.