While Word can do even complex calculations, they're far less straightforward than using Excel.
To see how to do a wide range of calculations in Word, check out my
Microsoft Word Field Maths Tutorial:
https://www.msofficeforums.com/word/...-tutorial.html
To see how to do just about every date-based calculation you might want to in Word, check out my
Microsoft Word Date Calculation Tutorial:
https://www.msofficeforums.com/word/...-tutorial.html
Do read the document's introductory material.
A better solution, though, might be to use an external workbook for the calculations, then link that to your Word document (i.e. copy the Excel data, then use Paste Special>Paste Link. Linking provides a number of display formats you can choose from and allows you to keep the document up to date with changes in the workbook.