With the blogosphere being so large and sitting in on webinars all over the world I often have trouble remember what the time difference is for me compared to the host sites.
There are several tools that are available out on the web to choose from and here are a few that are my favourite for ease of use.
http://www.timezoneconverter.com/
http://www.timeanddate.com/worldclock/converter.html
http://www.worldtimeserver.com/