Oh, so the boats weren’t in the same time zone as GMT?
>> so the boats weren’t in the same time zone as GMT? <<
Correct. The local time zones in the Persian Gulf are several hours ahead of GMT.
But military, aviation and diplomatic communications will normally cite time in the UTC or “Zulu” format, regardless of whatever time zone the locals happen to be in.
Anyway, a clock set on UTC gives the same time as a clock set to GMT. So whenever it’s 5:30 p.m. at the Greenwich Observatory in England (ignoring the UK’s use of daylight savings time), it’s 1730Z worldwide for the military.