The ISOWEEKNUM function in Google Sheets is a valuable tool for extracting the ISO week number from a supplied date. This function adheres to the ISO 8601 standard, which defines the first week of the year as the week containing the first Thursday. By allowing users to easily determine the associated week number, ISOWEEKNUM proves essential for various applications, from scheduling and reporting to data analysis.

Syntax

ISOWEEKNUM(date)

• date: The date for which the ISO week number is to be calculated. This can be a cell reference, a date string, or other date formats recognized by Google Sheets.

Example #1

ISOWEEKNUM("2023-01-05")

will calculate the ISO week number for January 5, 2023. The result will be 1, as this date falls in the first week according to ISO standards.

Example #2

ISOWEEKNUM(A1)

where A1 contains the date “2023-03-18” will return 11, indicating that March 18, 2023, is in the 11th ISO week of that year.

Example #3

ISOWEEKNUM("2021-12-31")

results in 52, indicating that December 31, 2021, falls in the 52nd week of the year according to ISO standards.

Error handling

• VALUE! – This error occurs if the input date is not recognized as a valid date format by Google Sheets.
• NUM! – This error appears if the provided date falls before the year 1980, as ISO week numbers are defined only from that year onward.

Conclusion

In summary, the ISOWEEKNUM function is an indispensable feature available in Google Sheets for users needing to align their date data with ISO week numbering. By simplifying the process of retrieving week numbers, this function enhances productivity and accuracy in various tasks ranging from project management to time-sensitive analysis. Understanding its syntax and handling potential errors ensures a smoother experience when working with date functions in Google Sheets.