I think this is because there is no Daylight Saving Time (DST) in Nuku'alofa so therefore for half the year when it is DST in England it is 13 hours ahead.
13 hours
GMT + 8 hrs = EST + 13 hrs
What is the time in Amman in 10 AM in GMT?
The east coast is GMT +10 hours Central is GMT +9.5 hours The west coast is GMT +8 hours
Bangkok is 7 hours ahead of GMT.
six hours apart. GMT is 6 hours ahead of CST.
Pakistan is normally 5 hours ahead of Greenwich Mean Time (GMT+5), but during daylight saving time, it is 4 hours ahead (GMT+4).
delhi is 5 hours and 30 mins plus from GMT
the same time as GMT
The east coast of Australia is at GMT +10 hours The west coast of Australia is at GMT +8 hours Beijing is at GMT +8 hours
The country that is 12 hours behind GMT is American Samoa.
it is gmt+7 hours means it is 7 hours ahead of standard gmt