Here write DATEDIF A1B1d A1 being the cell with start date and A2 with the end date It will output the number of days between the two dates. Excel has special functions to calculate the average of the number in a range of cells and also calculate the average of cells based on specified criteria like AVERAGE and AVERAGEIF functions. To calculate a column average supply a reference to the entire column.
To calculate the number of days in a given month from a date we need to use a formula based on EOMONTH and DAY.
This will calculate the average of all of the numbers in that range of cells. Use the Analysis Toolpak to calculate the moving average of a time series in Excel. Pointers about the NETWORKDAYS function Negative return value If the start date is later than the end date the function will return a negative value. In this formula the B2B15 is the Birthday column C2C15 is the Age column 12 is the specified month December which you will average by and you can change them based on your needs.