i don't know what ending up "in banters" means, but it doesn't sound very nice
switching time zones is easy, its a simple as adding or taking away a number from the hour; and maybe adding or taking away 30 if you are dealing with India, Iran, Newfoundland and a bunch of other places that insist on being awkward for some reason that's probably very valid but annoying to the rest of the world. As far as maths goes: its quite simple for most of the year, other than the times when the clocks change in and that's because America insists on being awkward. Having a clock on the forums wouldn't fix the guys problem which is that people would still schedule events using their local timezones, and the clock would run off server time which is in CET which I doubt is used by many on these forums. One solution that comes to mind to make things easier would be to give the time in both GMT and a local timezone (IST probably would be the one most used here), I've seen that done in other places and it makes things easier to convert.