I've just changed the way that GPSLog Labs detects the local timezone for a log to make it more reliable.
Each place now has a timezone field and this is used to set the default timezone for any logs to or from that place (kind of obvious really...)
I have been able to fill in most timezones for places that have been created to date. Have a look at the Places configuration page though as you may have one or two that you'll need to set yourself.
If a log doesn't match any places it will default to the timezone you've set in your Profile page, and the timezone for a log can always be edited if you want it to be something different.