WEEKNUM

WEEKNUM(date)

The week of the year a date falls in, counting the week that holds 1 January as week 1 and starting each week on a Sunday, as Excel's WEEKNUM does by default. It is not the ISO week number, and it has no second argument to change the start of the week.

Arguments

ArgumentWhat to give it
dateA date, like [Start date]. Blank gives blank.

Examples

Formula
=WEEKNUM([Start date])

The week of the year the task starts in.

Formula
=YEAR([Start date]) & "-W" & WEEKNUM([Start date])

A label for the week, with its year, to group tasks by.

Formula
=WEEKNUM([Start date]) = WEEKNUM(DATADATE()) AND YEAR([Start date]) = YEAR(DATADATE())

TRUE for tasks starting in the same week as the data date.

Reach for something else when

You wantUse
Totals or counts per week over timePERIODS with "week", whose weeks start on the project's week start
The day of the weekWEEKDAY
A label for the week's first dayTEXT: "Week of " & TEXT([Start date], "d mmm")