Calculating Elapsed Time with Excluded Periods

Mahesh can figure out how to calculate the difference between two dates and times in minutes. However, he would like to calculate the difference in minutes, yet exclude the hours between 5:00 pm and 8:00 am as well as excluding everything between 5:00 pm Friday to 8:00 am Monday. For example, if the first date is 02/18/09 6:00 pm and the end date is 02/19/09 9:00 am, the correct result should be 60 minutes. Mahesh wonders if this possible to do with a formula.

As should be obvious, a formula to achieve the desired result could be very complex. Many subscribers provided different solutions, including some great user-defined functions. Rather than focus on all of them, I figured I would just jump right to the most elegant (shortest) formula and suggest using it.

Assume that your starting date/time was in cell A1 and the ending date/time was in cell B1. Given these you could use the following formula:

=(NETWORKDAYS(A1,B1)-1)*("17:00"-"08:00")
+IF(NETWORKDAYS(B1,B1),MEDIAN(MOD(B1,1),"17:00"
,"08:00"),"17:00")-MEDIAN(NETWORKDAYS(A1,A1)
*MOD(A1,1),"17:00","08:00")

This is a single formula; it returns an elapsed time. This means that you will need to format the cell to show elapsed time. If you prefer to have the result as a regular integer, then you should use this version of the formula, instead:

=((NETWORKDAYS(A1,B1)-1)*("17:00"-"08:00")
+IF(NETWORKDAYS(B1,B1),MEDIAN(MOD(B1,1),"17:00"
,"08:00"),"17:00")-MEDIAN(NETWORKDAYS(A1,A1)
*MOD(A1,1),"17:00","08:00"))*1440

The change (multiplying the original result by 1440) results in a number of minutes rather than an elapsed time. The value 1440 is derived by multiplying 60 by 24 to get the number of minutes in a day.