(Sometimes called GMT Greenwhich Mean Time - not exactly the same but close enough)
GMT and UTC are exactly the same. Confusion arises because half the year the United Kingdom is on summertime, but this is simply GMT+1 or UTC+1. The only reasons for having two names are political, not practical.
Actually Alef, here you are mistaken

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For most applications, GMT and UTC are considered close enough not to worry about, but there
is a difference between the two. Not important for Fibs players but if you are using a GPS for observations of some kind it is critical.
Greenwich Mean Time is a time scale based on the apparent motion of the "mean" sun with respect to the meridian through the Old Greenwich Observatory (zero degrees longitude. 'Mean' sun is used because at certain times of the year, the sun will appear to move faster or slower through the sky due to the eccentricities of the earth's orbit.
UTC was introduced when scientists calculated the exact length of a second through the use of atomic clocks. 86,400 seconds = 1 full day. Again, due to the oddities of the earth's orbit, 86400 seconds doesn't always match the length of an actual solar day. So every 18 months or so, a 'leap second' is introduced to roughly synchronised with the earth's orbit.
There
is a difference between UTC and GMT! It is always kept at less than .9 of a second because of the leap second adjustment system however.
It has nothing to do with politics, and everything to do with scientific accuracy.