Which Century Is It?
How does SAS recognize date values such as "01DEC00"? Is this year 2000 or year 1900? By default SAS V8 recognizes two-digit years from 20-99 as 1920-1999 and 00-19 as 2000-2019. You may change this default with the system option YEARCUTOFF. This option can alter the cutoff year which is, by default, 1920.

Options Yearcutoff=1901;

Put this in your program before you start working with dates. In this example, the two-digit years from 01-99 are 1901-1999 and 00 is 2000.