We say “Καλημέρα” from dawn until 12:00, in both formal and informal settings. “Καλημέρα” can be used until about three o’clock in the afternoon, instead of “Χαίρετε”.

You can use this greeting from 12:00 until about three o’clock in the afternoon. Nowadays people tend to skip “Χαίρετε!” and say “Καλημέρα!” or “Καλησπέρα!” instead.

We say “Καλησπέρα” after 12:00, until late in the evening. If you enter a shop at half past two in the afternoon, you will say “Καλησπέρα”. If you arrive at a gathering just before midnight, you will still say “Καλησπέρα”.

It means both “Hello!” and “Goodbye!”. You can use it any time of the day. This greeting is informal, but using the plural “Γεια σας!” will make it sufficiently polite.

People say “Γεια μας!” (Cheers!) when they clink their glasses. This is a toast, not a greeting.