Django using admin datepicker in a custom form

Question

I am trying to use a Django admin datepicker in a custom form. It is displaying alright but I can only pick from the current year we are in. I want to be able to pick earlier years too. How can I use these earlier years with datepicker?

#my form.py

from django.forms.extras.widgets import SelectDateWidget
class ContactForm(forms.ModelForm):
    class Meta:
        model =contacts
        fields = ('First_Name','Middle_Name','Last_Name','Date_of_Birth','Gender','Island','Province','Date_of_Baptism','Congregation','Status','Comments',)

        widgets = {'Date_of_Birth': SelectDateWidget(),'Date_of_Baptism':SelectDateWidget()}