Greece is GMT + 2 . That means if its noon in London or Greenwich, England then its 2 PM here in all of Greece.
If you are in NYC and its noon, then its 7 hours later, or 7 PM here in Greece, except if Greece goes to daylight savings time by "falling ahead" and the US hasnt yet in which case it will be 8 hours ahead in Greece instead of 7. This event watched by astronomers all over the world usually takes place in October and can last for up to 3 weeks!
©Harry's Greece Travel Guides