How to Calculate Days Between Two Dates in Microsoft Excel Using DAYS

Tracking timelines, billing cycles, project milestones, and contract expirations requires calculating the exact interval between calendar dates in Microsoft Excel. Because Excel stores dates internally as serial numbers starting from 1 January 1900, finding the difference in days is straightforward. Depending on whether you need a dedicated function, simple formula subtraction, or working day calculations, Excel provides versatile methods to measure date differences accurately.

Calculating Days with the DAYS Function

The DAYS function is purpose-built to calculate the number of days between an end date and a start date without worrying about formatting anomalies.

=DAYS(end_date, start_date)

To implement the formula in your spreadsheet:

1. Ensure your dates are formatted properly in separate cells (for example, Start Date in A2 and End Date in B2).
2. Select the destination cell (e.g. C2) and enter: =DAYS(B2, A2)
3. Press Enter.

Note that the end date must be placed first in the argument list. If you reverse the dates (e.g. =DAYS(A2, B2)), Excel will return a negative integer indicating that the start date precedes the end date.

Calculating Days Using Simple Arithmetic Subtraction

Because Excel treats each calendar day as a whole integer increment, you can calculate day differences through direct mathematical subtraction:

=B2 - A2

If the calculated result unexpectedly displays as a formatted date (such as 15/01/1900) instead of an integer count, the cell has inherited date formatting. To correct this, select the formula cell, open the Number Format drop-down menu on the Home tab of the ribbon toolbar, and switch the format to General or Number with zero decimal places.

Calculating Workdays Excluding Weekends and Public Holidays

If you are measuring project duration or employee attendance, calendar days may overstate working time. The NETWORKDAYS function excludes Saturdays, Sundays, and optional declared holidays:

=NETWORKDAYS(start_date, end_date, [holidays])

For example, if cell A2 holds the start date, B2 holds the end date, and range E2:E5 contains dates of scheduled public bank holidays, use:

=NETWORKDAYS(A2, B2, E2:E5)

This returns only active business days, providing realistic timeline tracking for project management.