<p>Is there some simple way to calculate a Weeknumber value from a date value stored in XML?</p>

<p>It needs to be pure XSLT solution. I cannot use any code :(</p>

I program in Visual Basic, so I know how to do it using VB.NET.  Read your XML date into a variable (let's call it
SomeDate
).  Then you construct a new date that you
know
is the beginning of the year that contains your unknown date.  Then, you let the
DateDiff
function do its work to tell you the week number.
```
```
Dim SomeDate As Date = ReadDateFromXML()
Dim YearStart As New Date(Year(SomeDate), 1, 1)
Dim WeekNumber As Integer = DateDiff(DateInterval.WeekOfYear, YearStart, SomeDate)
```
```