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.

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, ...

The EOMONTH function in Microsoft Excel returns the last day of a month in the past, the current month, or a month in the future. Whether you need to calculate end-of-month due dates, deadlines, ...