Rorkes Drift, or any drift, no Paul.
Zulu Time is good old fashioned GMT. Greenwich Mean Time.
Or at least it was until all this time malarky was amended a few years ago. UTC blah blah...
GMT itself becomes confusing when the UK itself, with the 0 degree longitude at Greenwich, amongst a thousand and one other places, changes its clocks twice per annum from GMT to BST, British Summer Time, in March for Springtime when the clocks spring forward and 1 hour is lost, then reverts to GMT, back 1 hour, in October, for what we in the UK call Autumn. Rather amenable to the US terminology Fall frankly.
So, in summary, it is all rather a bit of caveat emptor as you are no doubt interested in Zulu time as noted in Naval Signals and reports, then trying to correlate those Zulu times against other Time Zones which will always be upto + or - 12 hours.
Can get messy.
Incidentally, i have NO idea how many other Countries change their clocks seasonally as in the UK.
None if they have their heads attached. It is a real pain in the...
A full broadside. The traditional English salute.