As a result, using the WEEKDAY function to calculate days of the week for dates in 1900 before March 1 yields incorrect results in Microsoft Excel worksheets built using the 1900 date system.

If Microsoft Excel does not recognize dates, then there is something wrong with the formatting. Use any of the methods mentioned here to format cells perfectly.

Excel has over 475 formulas in its Functions Library, but we've selected the most popular, from date and time functions to mathematics and simple data manipulation.

Formulas are powerful tools for performing calculations and analyzing data in Excel. In this beginner’s guide, you’ll learn how to use formulas and explore some popular built-in functions.

One way to correct this behavior is to change your default date system. On the Mac version of Excel, you can do this within the calculation pane of Excel's preferences.