I like the idea of the calander having an automatic timezone converter. When you enter the start time of an event there is also a field for timezone, which default to your local timezone. Then the calander can accurately show the TIME and DATE of the event.
This will have the benefit of showing
1) The order that events occur in
2) Highlighting event clashes.
As there is already a clock with, PDT, EDT, GMT, BST and AEST on the website it may not be much more effort to do this.
Currently I use the convention of entering the GMT time into the time field in the forum. But as other users are in different timezones they commonly enter their own local time into this field. If the system automatically converted the times it would be a "Lucinda" send.