iOS Question Get numberofweek with first day = monday

[schimanski]

I tried both subs to get the number of the week of the year. But the result of the following dates ist always week 5. The reason seems to be the start of the week = sunday, and not monday.
How can I set the first day of the week in one of the following subs?

Log(GetWeekNumber(1580030262356) & ", " & DateTime.Date(1580030262356) & " - " & DateTime.Time(1580030262356))
Log(GetWeekNumber(1580548662356) & ", " & DateTime.Date(1580548662356) & " - " & DateTime.Time(1580548662356))

5, 26.01.2020 - 10:17:42 = it's a sunday and in germany week 4
5, 01.02.2020 - 10:17:42

Private Sub GetWeekNumber(DateTicks As Long) As Int
    Dim psCurrFmt As String = DateTime.DateFormat
    DateTime.DateFormat = "w"
    Dim piCurrentWeek As Int = DateTime.Date(DateTicks)
    DateTime.DateFormat = psCurrFmt
    Return piCurrentWeek
End Sub

'-or-

Sub GetWeekNumber(ticks As Long) As Int
    Dim offset As Int = DateTime.GetDayOfWeek(DateUtils.SetDate( _
     DateTime.GetYear(ticks), 1, 1)) - 1
    Return Floor((DateTime.GetDayOfYear(ticks) -1 + offset) / 7) + 1
End Sub

Thanks for help

 

[Erel]

Sub GetWeekNumberStartingFromMonday (ticks As Long) As Int
    Dim firstdayOffset As Int = DateTime.GetDayOfWeek(DateUtils.SetDate( _
     DateTime.GetYear(ticks), 1, 1)) - 2
     If firstdayOffset < 0 Then firstdayOffset = firstdayOffset + 7
    Return Floor((DateTime.GetDayOfYear(ticks) - 1 + firstdayOffset) / 7) + 1
End Sub

 

[schimanski]

It works! Thank you very much...