If two digit year(yy) supplied in DateFormat or DateFormat, BasicDatePicker will add 1900 to year if above value or 2000 if below.
Amount to add to 1900 or 2000. Default value is 50
If yy = 05, then year = 2005 If yy = 55, then year = 1955
BasicDatePicker Class | BasicFrame.WebControls Namespace