Time zone confusion

We had a conference call planned at 8:00am. Reva was to join in from India. We got on to the call, and were done by 8:40am.
9:10am: SMS. Waited in conference now off to lunch
9:56am: Mail. You didnt initiate the call!
10:03am: Reply. I guess you dialled in at 9am UK time. We had the call at 8am.
3:17pm: Mail. I dialled at 8 GMT = 13.30 IST ? Correct?
3:19pm: Reply. Ah, no. We’re 4.5 hours ahead.
3:25pm: Mail. Great Britain is one hour ahead of GMT during summer!
3:53pm: Reply. Yeah, you’re right — most people don’t realise Greenwich isn’t always on Greenwich Mean Time 🙂