Validate Gregorian.moment() options. An error is now given

Pre 1.20 I was doing this

var now = Time.Gregorian.moment({:year=>0,:month=>0,:day=>0}); //Moment with value of 0

With 1.20 I now get

Failed invoking <symbol>
Invalid Value
@PC = 0x0
@PC = 0x300011c9
@PC = 0x10003dc4
@PC = 0x1000065e

I noticed this in the 1.20 whats new :

Validate Gregorian.moment() options. An error is now given when invalid values are given for the date.

So what are valid values?