The phrase "ahead of gmt" is correct and usable in written English.
It can be used to indicate a time zone that is ahead of Greenwich Mean Time (GMT), often in the context of scheduling or timekeeping.
Example: "The meeting is scheduled for 3 PM ahead of GMT, so please adjust your calendars accordingly."
Alternatives: "GMT+X" or "in advance of GMT".
This meant that during these summers the UK was two hours ahead of GMT.
It is now 8 hours and 30 minutes ahead of GMT (a change of 30 minutes).
In the interim we've experimented with permanent summer time (always one hour ahead of GMT) and even double summer time (always two hours ahead).
Jim realised that when they returned to the Lake District it would be going dark too early for his liking, so he decided to stick with European time, an hour ahead of GMT.
Late on Monday, an elevated road in downtown Hong Kong west of Admiralty remained packed with protesters (Hong Kong is eight hours ahead of GMT, 12 hours ahead of US eastern time,) and reporters at the scene around midnight said more were arriving.
And France used to be on Paris time, nine minutes ahead of GMT.
The statement added that a "rigorous search policy" will be in place ahead of the 15:00 GMT kick off in Perth.
The next vote will start at 16:00 GMT until 17:25 GMT, ahead of the final vote during BBC Radio 5 live from 20 00 GMT.
With a few exceptions, countries or regions simply choose a time zone that corresponds with their longitude: those east of Greenwich, in London, are usually ahead of Greenwich Mean Time (GMT), whereas those to the west are behind.
On Sunday 29 March the clocks go forward one hour ahead of Greenwich Mean Time (GMT) to mark the start of British Summer Time (BST), also known as Daylight Saving Time.
At 1am on 30 March, civil time in the UK will be fast-forwarded one hour ahead of Greenwich Mean Time (GMT), heralding longer, lighter evenings and, hopefully, the tentative beginnings of summer.
