Could someone explain me, why I get 12 Februray when running the code below?
I saw the days are from 1 to 31, only the months starts with 0
var d = new Date(2100,1,13)
> d
Fri, 12 Feb 2100 23:00:00 GMT
EDIT:
And why this time?? 23:00:00 it should be 00:00:00
Your locale timezone is interfering. Try:
new Date(Date.UTC(2100,1,13)).