[time-nuts] GMT vs. UTC

[jayh6 at verizon.net]

>GMT means many different things over time.  Once upon a time it did
>mean "whatever those silly celestial bodies, especially the sun, are
>doing over that quaint little town of Greenwitch." 

As is pointed out in my previous link, GMT varied from mean solar time to siderial observations in several different ways, all a but different.

I remember (hopefully correctly) that at one point, they built a new observing instruement a few hundred feet from the original. The legal term seemed to imply that the time was tied to the Sun passing the instrument, which would of course, invalidate every map in the world.