that will only affect !time, and leave the timestamps on the last seen on alts, whois, the log, the afks the roster along with several other things unchanged and still using UTC

so change where you can find gmdate()

would it be possible to add a preference to members so they can set their offset from GMT and the bot will remember it?

Yes, and no. The problem is daylight savings time. There are (obviously) 24 different offset, but UTC offset is not the same as a time zone. Each time zone has different rules, such as Daylight Savings Time (USA), and European Summer Time, etc.

For example, I'm currently in the US Central time zone. The standard (CST) offset for this zone is -6. Currently we are under Daylight Savings Time rules, so we are under Central US Daylight Time (CDT), not CST. Now the lower 48 states have 4 different time zones (Eastern, Central, Mountain, Pacific). Should be easy right? No so much, there are states such as Arizona that do not follow Daylight Savings Time rules. Arizona is always Mountain Standard Time. To add another layer of complexity the Navajo Nation Reservations do follow the DST rules, so if you are in Arizona but are on the Navajo Nation Reservation you are (Today: 2008-08-15) on MDT.

To add more confusion, time zone rules are in flux. The current USA Energy Bill changed the rules for daylight savings time for 2007 and 2008, but these provisions expire in 2009 and the old rules will take effect again unless the 2009-2010 energy bill renews them.

As time zones are political in nature situations like this can simply be expected. PHP does have some functionality for figuring out time zones, but again, time zones are political. If the politicians change the rules PHP itself needs to be updated. Previoulsy, some older versions of PHP4 were completely unaware of the 2007-2008 US rule changes, while some PHP4 installations were not. To work around this, the BeBot developers would have had to know what the status of each PHP version is in terms of time zone rules, and create code to correct PHP's outdated rules if the bot was running on an older PHP version. A similar situation is likely on PHP5 if the US changes daylight savings times rules again.

After doing through research on the whole mess I opted for the easy way out and went with UTC time, which is an internationally recognized standard. Even though UTC is the international standard for time, the freaking Europeans can't figure out the difference between UTC and European Summer Time. People in London will often give the GMT/UTC time as being an hour ahead of the actual UTC time, and then tell you that they are right and you're wrong. Sorry guys, it's you who are screwed up not the rest of the world. European Summer Time is UTC+1 if you're in the +0 offset time zone...

So even the international standard for time is often confused and given incorrectly. Airline Pilots, ship captains, and computer programmers are generally the only people to get it right. 

So basically we've written off the whole timezone thing as way too much effort. Thank your local, national, and international politicians.

Gee whiz people, whats so hard about figuring out your time zone from the UTC?  If you use UTC as your standard when setting up events and raids, then everyone is on the same sheet of music.