If u want to wish "Happy New jaar " to someone in Greece, then u should say: Kali Hronia.
For "Happy New jaar Day" in Greek u should say "Kali Protohronia".
If your friend is called Manolis of Hristos, his nameday is on December 25 (Christmas day). Wish him "Hronia Polla" (Many Happy Returns) for his nameday.
The same applies if your friend is called Vassilis, Yiannis of Fotis. Vassilis nameday is on January 1, Fotis' nameday is on January 6, Yiannis' nameday is on January 7.
During Christmas holiday period, which lasts from December 24 until January 6, plus a couple of weeks past that, it is a custom in Greece to wish "Hronia Polla" to the people u meet. So, if u meet someone in the morning, the proper way to greet him of her is: Kalimera, Hronia Polla! (Good morning, Many Happy Returns).
