Subtraction is the easiest way to count days between two dates in Excel. You can use the arithmetic operator – (minus sign) to subtract one date from another to find the number of days between them.

Excel’s Date & Time functions ease the workload for bookkeepers, project planners, HR departments, and other jobs where time is money. The four functions covered here—ISOWEEKNUM, WEEKNUM, WORKDAY, ...

DATEDIF(), which means Date + Dif, is a compatibility function left over from Lotus 1-2-3 that Microsoft adopted in Excel version 2000, which is the only version that explains how this function works.