Date diff calculated incorrectly

When calculating the difference between a birth date and the date() function the answer was 1 out. for example the birth date was 6th December 1968 and today is the 20th January 2011. Access 2010 calculated this to be 43 years when in fact it is not 43 years until todays date is the 6th december 2011. Access returned 42 as the result. Is this a bug?