The DATE function creates a valid Excel date using individual year month and day components. In cell C2 enter A2B2 and copy down as needed. If the year is between 0 and 1900 Excel will add 1900 to the year.
IF B1.
Each day counts one. When you specify the year month and day Excel produces a serial number that can then be formatted as a normal looking date. The Excel DATE function combines three values to create a date. For example DATE 100 12 31 returns December 31 2000 1900 100.