干杯 mostly means "Bottom Up" instead of "Cheers".
干杯 is in fact "Cheers". It is also "bottom up".
If you say 乾杯 to someone in taiwan or china it means to finish everything in the glass, so it is closer to bottoms up.
Why does 新年好 change to 新年快乐 when used with 干杯? Both seem to translate to "Happy New Year!".