元旦和跨年怎么说英语

"元旦" (Yuándàn) is the Chinese term for New Year's Day, which is celebrated on January 1st. In English, it is simply referred to as "New Year's Day."
"跨年" (Kuànián) is the Chinese term for New Year's Eve, which is the day before New Year's Day. In English, it is commonly referred to as "New Year's Eve."
So to wish someone a happy New Year in English, you could say "Happy New Year" or "Happy New Year's Day." To wish someone a happy New Year's Eve, you could say "Happy New Year's Eve."