The same way you would do so to anyone else.
These are common greetings from New Year, Christmas or Thanksgiving day. Examples Happy Christmas, Happy New Year or Merry Christmas. You could also say Happy Holidays.
Sending out Christmas cards is far more common than sending out a New Year Greeting card. It is fair to say that many people send out Christmas greetings, and less people send New Year greetings. However, there are in-store and online resources for those who do choose to send New Year cards.
A common greeting in Hawaiian is "Aloha." It is used to say both "hello" and "goodbye," as well as representing love, peace, and compassion.
In Russian, you can say "здравствуйте" (Zdravstvuyte) or "привет" (Privet) to greet someone.
Season's Greetings in Portuguese is "Felizes Festas" or "Boas Festas".
Mele Kalikimaka - Merry Christmas (translation of the english) Hau'oli Makahiki Hou = Happy New Year
Bonne Annee ! This means have a good new year, because that's what they celebrate. The french don't take that much notice of christmas, but if forced they say Joyeux Noel.
Greetings from Germany (English) Grüsse aus Deutschland (German)
gbiresih
Saudações
Sawerticka
Australians speak english, unless of corse aboriginal. so you would say seasons greetings.