To subtract dates in Excel, simply enter the following formula: "=A3-A2", assuming that cells A3 and A2 contain the dates that need to be subtracted. This will output the difference between the two dates, expressed in days.
Excel also allows one to compute this difference expressed in workdays, months or years. The expression "=NETWORKDAYS(A2,A3)" will calculate the number of working days between two dates. The difference in months will be given by the formula: "=MONTH(A3)-MONTH(A2)", if the two dates fall in the same year. If they are more than a year apart, the expression needs to be changed to: "=(YEAR(A4)-YEAR(A3))*12+MONTH(A4)-MONTH(A3)". Finally, the difference in years can be computed using the following formula: "=YEAR(A3)-YEAR(A2)".