Often times, a project manager will be given a project’s start date and the number of days it should take to complete. Considering, however, that most people work Monday through Friday, you can’t simply add a certain number of days to the starting day’s date to come up with your ending date, because that wouldn’t take into consideration weekends and holdiays.
Using the formula =WORKDAY() allows you to specify a beginning date, the number of work days until the ending date, and any holidays that might fall between the start and finish of the project.
If you wish to specify holidays, enter the holiday’s date value in the formula (i.e. Memorial Day in 2009 is May 25, 2009, or in Excel’s number format, 39958). This can be determined by using Excel’s =DATE() formula.
More on these formulas can be found on our Wiki page.