WEEKDAY Function
Returns the day-of-week number for a date.
Syntax
Parameters
| Parameter | Description | Required |
|---|---|---|
| serial_number | The date serial to evaluate. | Required |
| return_type | Optional. Controls numbering: 1 (default) = Sunday=1 to Saturday=7; 2 = Monday=1 to Sunday=7; 3 = Monday=0 to Sunday=6; 11-17 select a specific start day (11=Mon start ... 17=Sun start). | Optional |
Basic Example
Day of week for New Year 2024
=WEEKDAY(DATE(2024, 1, 1))2024-01-01 is a Monday. With the default return_type 1 (Sunday=1), Monday is 2.
Advanced Examples
Example 1: Monday-based numbering
Wanting 1 = Mondayreturn_type 2 renumbers the week
=WEEKDAY(DATE(2024, 1, 1), 2)Example 2: Zero-based Monday numbering
Programming-style 0-6 weekreturn_type 3 gives Monday=0
=WEEKDAY(DATE(2024, 1, 1), 3)How WEEKDAY Works
WEEKDAY computes the day of the week from the date serial using modulo-7 arithmetic, then maps the result to a number according to return_type. The default (1) treats Sunday as the first day (1) and Saturday as the last (7).
Important Notes & Limitations
return_type must be one of 1, 2, 3, or 11-17; other values return #NUM!.
The time portion of a date-time serial does not affect the weekday.
It works only for dates Excel supports (1900-01-01 onward).
Common Errors & Fixes
#NUM!An invalid return_type value was supplied.Fix: Use 1, 2, 3, or 11-17.
#VALUE!The date argument is text Excel cannot parse.Fix: Convert the text to a real date serial first.
Download Practice File
WEEKDAY
weekdayPractice WEEKDAY with Real Data
Download a sample CSV file with pre-populated data and practice exercises for the WEEKDAY function. Works in both Excel and Google Sheets.
File format: CSV (comma-separated values) - opens in Excel, Google Sheets, and all spreadsheet apps