The DAYS function is a date and time function which returns the total number of days which exist between two valid dates in Excel.

This is the format of the DAYS function:

=DAYS(END DATE, START DATE)

Here is an example of the DAYS function:

=DAYS(45067, 45054) = 13

This function is valuable when creating estimations and plans about any type of contractual work, or tracking progress on larger projects with time constraints. When paired with the TODAY function it can also be used as a running total against a specific task.

An example of a functional implementation of this would be creating a project tracker that will be used to aggregate the project information and stakeholders for a more transparent operation. In it will be the estimated start and end dates for each task and subtask in the project. To have an idea of the manhours required the dates are used to simulate resource investment by each party.

ex: Start dates are located in column D, end dates are located in column E, and table data begins in row 12

=DAYS(E12,D12)