Note: This clock is assuming that most countries have a Daylight Saving Time (during daylight saving periods, England is at GMT+1 where it should be at +0, all other time zones are affected the same way.) To have the proper GMT difference you should do a -1 on the GMT number during those daylight saving periods. A lot of sources with timezones maps were found, but all of them have differences (mainly in Asia). So the bondaries of timezones are approximate. You must always consider that the time you receive may be one hour early or late. To have the precise difference in time zone, you should go to the country's page or check this time zone website.
This clock system was provided by Virtual Max.