1. It would be humanely impossible to determine the yyyy range that you need to provide for the person whose dob you need. Instead of having multiple listitems, combos, and writing client side validation code..and letting loose some "Y2K" sort of bugs, i would sincerly suggest you to have a look at dateTime controls in built in ASP.Net toolkit or some thirdparty as the need be.
2. If you worried about formatting the date, then it should not be a worry. because you have the datetimeFormat and toString Overrides to take care of that.
for e.g. if the calendar returns "4/4/2009 12:00AM" ,
you could then use, calendarDateValue.ToString("MM/dd/yyyy") to get it in the right format you need.
3. If you follow the step above, then these problems would be automatically gone.