MS Excel: DAY function to extract day numbers from dates

Fakhriddinbek
May 3
2 min read

The DAY function in Excel is used to extract the day of the month from a given date. Whether you need to filter data by day, group records, or perform date-based analysis, the DAY function provides a simple way to isolate the numeric day (1–31) from a full date.

Excel window with function arguments dialog for DAY function. Toolbar options displayed above, and a blank spreadsheet in the background.

It’s especially helpful in time-based reporting, billing systems, and data cleaning tasks where day-level granularity is required.

Syntax

=DAY(serial_number)

Parameters:

Argument	Description
serial_number	Required. A valid Excel date or a cell containing a date.

Returns: An integer between 1 and 31, representing the day of the month.

Examples

Cell A2 (Date)	Formula	Result	Explanation
2025-05-02	=DAY(A2)	2	Extracts the day from the full date
15/10/2024	=DAY(A3)	15	Returns the 15th day
=TODAY()	=DAY(TODAY())	Varies	Gives today's day number dynamically
"March 8, 2023"	=DAY("3/8/2023")	8	Works with text dates if recognized

Excel stores dates as serial numbers; DAY will work on both actual dates and valid date serials.

Use Cases

Scenario	How DAY Helps
Grouping by day in reports	Extract day numbers for pivot tables
Calculating due dates or intervals	Subtract days between two dates
Creating date-based conditions	Use with IF, IFS, SWITCH, etc.
Validating data entry	Ensure correct day values entered

Notes

If the input is not a valid date, Excel will return a #VALUE! error.
If you're working with text that looks like a date, ensure it's parsed correctly or use DATEVALUE() to convert it first.

Related Functions

Function	Description
MONTH()	Returns the month number from a date (1–12)
YEAR()	Returns the year from a date
TODAY()	Returns the current date
DATE()	Constructs a date from year, month, and day
TEXT()	Can extract day using custom formatting "dd"

Summary

Feature	Description
Function Name	DAY
Purpose	Extract the day portion of a date
Result	Integer between 1 and 31
Argument Type	Valid date or date serial number
Compatibility	All Excel versions

Final Thoughts

The DAY function is one of Excel’s foundational date functions. It’s lightweight but powerful, particularly when paired with MONTH, YEAR, and conditional formulas for building dynamic, date-aware spreadsheets.