Validation of a date filed in MS access

I wish to create a field to store a date of birth, however I do not want it to accept a date either after to day or more than 120 years ago.

I know that now() gives me the current date, and that I can set the validation

between “a start date” and “an end date”

What I cannot figure out is how to make the start date to be 120 years before today.
Help – please!