WEEKNUM Function
Purpose
Returns the week number of a specific date in the year (an integer from 1 to 54), indicating where the week falls numerically within the year.
Syntax
EXCEL
=WEEKNUM(serial_number, [return_type])
Arguments Breakdown
| Argument | Required? | Description |
|---|---|---|
serial_number |
Required | The date within the week you want to find. |
return_type |
Optional | A number that determines on which day the week begins (defaults to 1 = Sunday). |
Return Types:
1(default): Week begins on Sunday.2: Week begins on Monday.21: ISO 8601 week number system (week 1 is the first week with 4+ days in the new year).
Practical Examples
1. Current Date Week Number Drill
From Formulas_&_Functions_Part_2.xlsx (Sheet Date and Time , cell D23):
EXCEL
=WEEKNUM(D8)
Where D8 contains =TODAY(). Answers the business question: "Ψ§ΩΨ£Ψ³Ψ¨ΩΨΉ ΩΨ§Ω
ΩΩ Ψ§ΩΨ³ΩΨ©Ψ" (Which week of the year does this date belong to?).
2. Standard Business Week (Monday Start)
EXCEL
=WEEKNUM(OrderDate, 2)
Ensures weeks start on Monday (aligning with international production cycles).
3. Retail Weekly Sales Variance
Comparing Week N this year vs Week N last year for retail benchmarking.
Return Type System Reference
- System 1 (Traditional): The week containing January 1 is Week 1.
1: Sunday (Default)2: Monday11: Monday12: Tuesday17: Sunday
- System 2 (ISO 8601 Standard):
21: The first week of the year containing at least four days (Thursday) is Week 1. Eliminates 1-day or 2-day partial week anomalies at year start.
Related Knowledge
- Notes: 06 Date and Time Intelligence
- Workbook:
11_Demos_and_Workbooks/03_Formulas_and_Functions/Formulas_&_Functions_Part_2.xlsx(Sheet:Date and Time)