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DAYS Function
Summary
The DAYS function calculates the exact number of calendar days between two dates, making it perfect for tracking project durations, age calculations, or any time span measurement in Excel.
Syntax
DAYS(end_date, start_date)Parameters
| Parameter | Type | Required | Description |
|---|---|---|---|
| end_date | Date |
Yes | End date for the calculation - must be a valid Excel date |
| start_date | Date |
Yes | Start date for the calculation - must be a valid Excel date |
Using the DAYS Function
Use DAYS when you need the actual calendar days between dates. Excel stores dates as serial numbers, so DAYS simply subtracts the start_date serial number from the end_date serial number. Perfect for deadlines, aging reports, and time tracking.
Common DAYS Examples
Basic Days Between Dates
=DAYS("15-MAR-2021","1-FEB-2021")Calculates 42 days between Feb 1 and Mar 15 (dates in quotes)
Cell Reference Example
=DAYS(A2,A3)Calculates days between dates in cells A2 (end) and A3 (start)
Project Duration
=DAYS(TODAY(),B2)Shows days since project start date in B2
Age in Days
=DAYS(TODAY(),C2)Calculates exact age in days from birthdate in C2
Frequently Asked Questions
Common Errors and Solutions
#NUM!
Cause: Date values outside Excel's valid range (1900-9999)
Solution: Use valid dates within Excel's supported range
#VALUE!
Cause: Text cannot be converted to dates
Solution: Check date format and use DATEVALUE if needed
Notes
- Positive result = end_date after start_date
- Negative result = end_date before start_date
- Excel dates start at serial number 1 (Jan 1, 1900)
- Available only in Excel 2013 and later versions
Compatibility
Available in: Excel 2013, Excel 2016, Excel 2019, Excel 365
Not available in: Excel 2010, Excel 2007, Excel 2003
Content last reviewed: December 9, 2025
Update frequency: As needed
Excel versions tested: Excel 2013+, Excel 2016, Excel 2019, Excel 365