Excel returns FALSE sometimes.... why

I'm using this formula to show the persons age based on date of birth. In some cases it works but in others it returns FALSE. If I change the date of birth it is a hit and miss as to whether it displays the age or FALSE. I need it to reflect the age all the time and leave the cell blank if no date of birth is displayed. Any assistance appreciated.

=IF(ISBLANK(F2),"",IF(MONTH(TODAY())>MONTH(F2),YEAR(TODAY())-YEAR(F2),IF(AND(MONTH(TODAY())=MONTH(F2),DAY(TODAY())>=DAY(F2)),YEAR(TODAY()))))