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