====== YearWeek(date) ======
Category:  Date and Time function

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=====Description=====
This function returns a time period formatted as year-ISO week number ("yyyy-W##"), or an error if the argument is not a number date.

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=====Arguments=====
^Argument^Type^Description^
|date|Date or Number (date serial)|A expression representing a date.  See "Remarks" below for details.|

**Return value type:** String

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=====Remarks=====
The //date// argument can take any value or expression that evaluates to a date serial value, with or without a time portion.  Examples include:  
  * A date string:  #2019-12-12
  * A date serial value: 43811 (the date serial for "2019-12-12")
  * A date value created using the [[syntax:functions:date|Date]] function: date("2019-12-12","yyyy-MM-dd").

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=====Examples=====

  yearweek(#2025-02-25)  //Returns "2025-W09"

  yearweek(44426)  //Returns "2021-W33" (44426 equivalent to August 18th, 2021)

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===== See also =====
  * [[syntax:functions:yearday|YearDay(date)]]
  * [[syntax:functions:yearquarter|YearQuarter(date)]]