How do I convert a calendar week into a date in Excel?

Question

I have a week number and a year, and would like to calculate the date of the Monday for that specific week in Microsoft Excel.

Year   Week   Date (Monday)
2012   1      January 2, 2012
2013   16     April 15, 2013
2014   42     October 13, 2014

What formula can I use to convert a calendar week to a specific date?

Answer 1

For ISO week numbers you can use this formula to get the Monday

=DATE(A2,1,-2)-WEEKDAY(DATE(A2,1,3))+B2*7

assuming year in A2 and week number in B2

it's the same as my answer here https://stackoverflow.com/a/10855872/1124287

Answer 2

The following formula is suitable for every year. You don't need to adjust it anymore. The precondition is that Monday is your first day of the week.

If A2 = Year and Week = B2
=IF(ISOWEEKNUM(DATE($A$2;1;1)-WEEKDAY(DATE($A$2;1;1);2)+1)>1;DATE($A$2;1;1)-WEEKDAY(DATE($A$2;1;1);2)+1+B2*7;DATE($A$2;1;1)-WEEKDAY(DATE($A$2;1;1);2)-6+B2*7)

Answer 3

If your week number is in A1 and the year is in A2, following snippet could give you dates of full week

=$A$1*7+DATE($B$1,1,-4) through =$A$1*7+DATE($B$1,1,2)

Of course complete the series from -4 to 2 and you'll have dates starting Sunday through Saturday.

Hope this helps.

Answer 4

如果周数在A1 ，年份在A2 ，您可以尝试：

A1*7+DATE(A2,1,1)

Answer 5

A simple solution is to do this formula:

A1*7+DATE(A2,1,1)

If it returns a Wednesday, simply change the formula to:

(A1*7+DATE(A2,1,1))-2

This will only work for dates within one calendar year.

Answer 6

If A1 has the week number and year as a 3 or 4 digit integer in the format wwYY then the formula would be:

=INT(A1/100)*7+DATE(MOD([A1,100),1,1)-WEEKDAY(DATE(MOD(A1,100),1,1))-5

the subtraction of the weekday ensures you return a consistent start day of the week. Use the final subtraction to adjust the start day.

Answer 7

=(MOD(R[-1]C-1,100)*7+DATE(INT(R[-1]C/100+2000),1,1)-2)

yyww as the given week exp:week 51 year 2014 will be 1451

Answer 8

If you are looking for the opposite to get a date from a weeknumber i found a solution online and changed it slightly:

Function fnDateFromWeek(iYear As Integer, iWeek As Integer, iWeekDday As Integer)
  ' get the date from a certain day in a certain week in a certain year
  fnDateFromWeek = DateSerial(iYear, 1, (iWeek * 7) _
          + iWeekDday - Weekday(DateSerial(iYear, 1, 1)) + 1)
End Function

I took the formular from asap-utilities.com/ and changed

DateSerial(iYear, 1, ((iWeek - 1) * 7) 

to

DateSerial(iYear, 1, (iWeek * 7)

Update

It seems that at least for germany the formular works not as expected for the leap year 2016 so i changed it to this

Function fnDateFromWeek(iYear As Integer, iWeek As Integer, iWeekDday As Integer)
' get the date from a certain day in a certain week in a certain year
  
    If isLeapYear(iYear) Then
        curDate = DateSerial(iYear, 1, ((iWeek) * 7) _
          + iWeekDday - Weekday(DateSerial(iYear, 1, 1)) + 1)
    Else
        curDate = DateSerial(iYear, 1, ((iWeek - 1) * 7) _
          + iWeekDday - Weekday(DateSerial(iYear, 1, 1)) + 1)
    End If
    fnDateFromWeek = curDate
End Function

Since 2016 hardcoded is not ideal you could check if a year is a leap year with this function

Function isLeapYear(iYear As Integer) As Boolean

    If (Month(DateSerial(iYear, 2, 29)) = 2) Then
        isLeapYear = True
    Else
        isLeapYear = False
    End If
    
End Function

For a non-leap-year DateSerial(iYear,2 ,29) returns 1st of march

This may still be wrong but my limited test gave the expected results:

Sub TestExample()
   Debug.Print Format(fnDateFromWeek(2014, 48, 2), "ddd dd mmm yyyy") ' mo 24 Nov 2014
   Debug.Print Format(fnDateFromWeek(2015, 11, 6), "ddd dd-mmm-yyyy") ' fr 13 Mar 2015
   Debug.Print Format(fnDateFromWeek(2016, 36, 2), "ddd dd-mmm-yyyy") ' Mo 05 Sep 2015
End Sub

Answer 9

I'm sorry but none of the solutions I could understand actually gave the correct result. In some instances the start of the week was after the actual date. ie the start date of the week for a Sunday was the coming Monday. Start of week error

I would appreciate if someone can correct my thinking. Thanks