That's Mandarin wishes a Happy New Year!
元旦快乐!
Yuándàn kuàilè!
Happy New Year!
You will also hear some people say:
新年快乐！
Xīnnián kuàilè!
元旦 (Yuándàn) • New Year's Day (January 1)
新年 (Xīnnián) • New Year (but it's also used to refer to Chinese New Year) (
快乐 (kuàilè) • happy; merry; joyful; cheerful
