other time zones are 0800 +5 where the 0800 refers to UTC and the +5 is what's needed to convert to local time.

I think it might be the other way around. I don't know if anyone here still uses good ol' Pine for email. I do, and it stamps emails as follows:

hh:mm:ss (-ttt)

The hh:mm:ss is local time of the person who wrote it, and the stuff in brackets is how to translate their time to UTC. Anyway, I figured the guys who programmed Pine probably followed some sort of standard way of telling time across time zones. Maybe, or maybe not.

*Edit: I take that back. Everyone else doesn't necesarily WRITE in Pine, but when I read in Pine, that info is there. So the mail servers are the ones which stamp it like that, I guess.