lammert - 11:30 am on Sep 8, 2010 (gmt 0)
I wouldn't store timezones in values, because you can't cope with daylight savings time that way. Better is to store the timezone as VARCHAR() and use the ASCII timezone identifiers. Most scripting languages have functions to convert UTC times to local times when you supply the timezone identifier.
If you are using PHP, a list of accepted timezones can be found here [php.net].