GMT, Greenwich Mean Time

• Greenwich Mean Time (GMT) originally referred to the mean solar time
at the Royal Observatory in Greenwich; now, it is for the most part,
the same as Coordinated Universal Time (UTC).
• until 1972 all world time zones were specified as an offset from GMT.
• since 1972 all official time services are synchronised to UTC.
• time zones still start at the Prime Meridian in Greenwich.

EXAMPLE: