You can work out the date so many days away in Excel, by just doing one date plus the number of days. This works because Excel treats dates as numbers (as long as you have actual dates, and not just text that looks like a date). However, if you are trying to calculate with working days this simple approach doesn’t work well. Fortunately, with WORKDAY, working with working days is easy.
When you are dealing with the number of workdays and start and end dates, then the function called WORKDAY is there to help. This will calculate the date, from a start date that is so many workdays away. The cool thing is you can even set the holidays that you want to not count as workdays, and it automatically ignores the weekends.
So, if you have a project that you think will take 25 workdays to complete, and you are going to start that on the first of March, what day will it be finished?
WORKDAY(start_date, days, [holidays])
As you can see the function requires two inputs and has the option for a third.
The first input needs to be a date, and the second the number of days away. These can either be typed into the formula, or more usually into a cell that the formula will reference.
To make use of the third input, you need to have a list of the holiday dates that you don’t want to be counted as workdays. Weekends are automatically ignored.
This mean that you can customise it to your location, even specifying regional holidays.
You just need to make sure you keep the list up to date and add the dates for the future holidays.
Back to our example.
When we use the workday function without the optional input it calculates that the finish day of the project will be 3rd April. When we use the third input (which is the list of dates of Good Friday and Easter Monday), it skips over those dates as working days and calculates that the project will actually finish on the 7th of April. Note that it only needs the actual dates, the labels “Good Friday” and “Easter Monday” are just there for our benefit so we know which holidays the dates represent.
So, to accurately calculate when projects will finish don’t forget about WORKDAY!