I am afraid that’s wrong. What you are calling GMT is actually called UT1. GMT does not exist as a separate thing any more. It was the timescale maintained by

I am afraid that’s wrong. What you are calling GMT is actually called UT1. GMT does not exist as a separate thing any more. It was the timescale maintained by the Greenwich observatory, but their timescale matched UTC since the rubber seconds era in the 1960s, and in 1972 Greenwich time became UTC with leap seconds. The Greenwich observatory as an institution does not exist any more (there’s a museum where it used to be but it isn’t a working national scientific laboratory). GMT is now an informal synonym for UTC that still appears in things like British law for historical reasons.