The birth date widget on Reports such as the Constituent Detail seems hard coded to allow only dates within the last 20 years. How do I adjust this?
Under Administer > Customize Data and Screens > Date Preferences you can adjust various date settings. In this case it's a little unclear but rather than changing the "Birth and deceased dates" setting you need to adjust the "searchDate" setting which is "Used in search forms and for relationships."
The "Start offset" value is the number of years prior to today that should be allowed in the datepicker.