"-0800 (GMT)" is very different from "-0800 GMT". It might seem subtle to you, but the latter is referring to -0800 in reference to GMT. Yes, this might seem redundant, but there's a difference between redundant and confusing. If anything, the GMT should make it *more* clear that -0800 is a timezone offset, not less.
mIRC does not list "-0800 (GMT)". If it did, I could see why this would confuse you into thinking "GMT" was the shortname for the timezone. This is not what mIRC is doing, since the GMT is not in parens.
