How many hours are between the Prime Meridian and the International Date Line?
Roughly you could say 12 hours, but there are no countries on the International Date Line. Every country the Prime Meridian passes through is not GMT, but for simplicity I’ll use it. West of the IDL would be GMT+12, east is GMT-12. It’s still a 12 hour difference, but the day will change one way or the other depending on the time GMT. If you want to see the countries that aren’t GMT, see this map: http://www.worldtimezone.
