When people are involved in a team from many different places and thus different time zones, you have two choices. Either everyone has to state any meeting times in their own time zone and then rely on everyone else to do the conversion to their time zone (which in my opinion, is pretty hard to get right all the time); or everyone agrees to use one time zone as the “universal time zone”. In the latter, everyone only has to remember one time zone conversion; from their time zone to the universal one.

What Do I Need To Do?
Encourage the adoption of a universal time zone within your project team. Either go for one where most of the people are based (West Coast USA, East Coast USA, London time, etc.), or go for a “major time zone” that is commonly known or can be easily seen on a Web site, eg, a news web site.

See A-Z of Virtual Teams: Summary for the complete list.