If tu want to wish "Happy New año " to someone in Greece, then tu should say: Kali Hronia.
For "Happy New año Day" in Greek tu should say "Kali Protohronia".
If your friend is called Manolis o 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 o Fotis. Vassilis nameday is on January 1, Fotis' nameday is on January 6, Yiannis' nameday is on January 7.
During navidad 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 tu meet. So, if tu meet someone in the morning, the proper way to greet him o her is: Kalimera, Hronia Polla! (Good morning, Many Happy Returns).
