How is the week number reset to 1 when the the first year is over, or for consecutive years

Question

Hi Good People,

How do I reset the week number to ( 1 ) when the year is over.
My start Date would be whatever the user chooses Lets say they chosen ( 01 01 2019, (dd MM yyyy) (week number ( 1 )

The Code I have for the first year is ...

(The date is selected by a Date Time Picker then the value selected, is put in a Textbox called ( TxtDateFinancialYearStarts )

 Dim startDate As DateTime = GetDateFromString(TxtDateFinancialYearStarts.Text)
 Dim newDate As DateTime = GetDateFromString(TxtDate.Text)
 Dim dateDif As TimeSpan = newDate.Subtract(startDate)
 Dim weekNo As Integer = (dateDif.Days / 7) + 1
 LBWeekNumber.Text = weekNo.ToString()

The first Year is OK.

'Then I Get Last Day of the Financial Year

        Dim lastdayOfYear As DateTime = DtpDate.Value.AddYears(1).AddDays(-1)
        TxtLastDayofFinancialYear.Text = lastdayOfYear.ToString("dd  MM  yyyy")

The last Day of the year also get put into another Textbox called ( TxtLastDayofFinancialYear.Text )

Here is where I want to check if the date has surpassed the Last day of the year ( 31 12 2019, ( dd MM yyyy )

Then here is where I want to reset the Week number to ( 1 ) if the Last day of the first year has been Surpassed. also for more consecutive years.

Can Someone please Help

Kind Regards
Gary

Sorry I forgot to add Code for getting date from string.

Function GetDateFromString(s As String) As Date
        Dim d As Date
        If Date.TryParse(s, d) Then Return d
        Return Now
    End Function

Answer 1

Hi
Maybe ............
Have a look at this to see if it helps. This example seems to deal with the task you are asking about.

I have not shown the changing of the FirstDayOfWeek, but if needed then it is trivial to test those variables out too.

The example uses a DataGridView named 'dgv' as shown below. I have set some test dates surrounding a leap year, but they can be editted to suit for testing.

'https://learn.microsoft.com/en-us/dotnet/api/microsoft.visualbasic.dateandtime.datepart?view=netframework-4.7.2&f1url=%3FappId%3DDev16IDEF1%26l%3DEN-US%26k%3Dk(Microsoft.VisualBasic.DateAndTime.DatePart);k(TargetFrameworkMoniker-.NETFramework,Version%253Dv4.7.2);k(DevLang-VB)%26rd%3Dtrue  
  
Option Strict On  
Option Explicit On  
Public Class Form1  
  
  Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load  
    With dgv  
      .Rows.Add("01 Jan 2023")  
      .Rows.Add("31 Dec 2023")  
      .Rows.Add("01 Jan 2024")  
      .Rows.Add("31 Dec 2024")  
      .Rows.Add("01 Jan 2025")  
      .Rows.Add("31 Dec 2025")  
    End With  
    Calc()  
  End Sub  
  Private Sub DataGridView1_CellValidated(sender As Object, e As DataGridViewCellEventArgs) Handles dgv.CellValidated  
    If e.ColumnIndex = 0 Then Calc()  
  End Sub  
  Sub Calc()  
    For i As Integer = 0 To dgv.RowCount - 1  
      If Not i = dgv.NewRowIndex Then  
        dgv(1, i).Value = DatePart(DateInterval.WeekOfYear, CDate(dgv(0, i).Value), FirstDayOfWeek.Monday, FirstWeekOfYear.Jan1)  
        dgv(2, i).Value = DatePart(DateInterval.WeekOfYear, CDate(dgv(0, i).Value), FirstDayOfWeek.Monday, FirstWeekOfYear.FirstFullWeek)  
        dgv(3, i).Value = DatePart(DateInterval.WeekOfYear, CDate(dgv(0, i).Value), FirstDayOfWeek.Monday, FirstWeekOfYear.FirstFourDays)  
  
      End If  
    Next  
  End Sub  
End Class  

Answer 2

@Gary Simpson , I think Calendar.GetWeekofYear is what you looking for
system.globalization.calendar.getweekofyear

Here same page sample in VB

Public Sub SampleGetWeek()  
    ' Gets the Calendar instance associated with a CultureInfo.  
    Dim myCI As System.Globalization.CultureInfo = New System.Globalization.CultureInfo("en-US")  
    Dim myCal As System.Globalization.Calendar = myCI.Calendar  
  
    ' Gets the DTFI properties required by GetWeekOfYear.  
    Dim myCWR As System.Globalization.CalendarWeekRule = myCI.DateTimeFormat.CalendarWeekRule  
    Dim myFirstDOW As DayOfWeek = myCI.DateTimeFormat.FirstDayOfWeek  
  
    ' Displays the number of the current week relative to the beginning of the year.  
    Console.WriteLine("The CalendarWeekRule used for the en-US culture is {0}.", myCWR)  
    Console.WriteLine("The FirstDayOfWeek used for the en-US culture is {0}.", myFirstDOW)  
    Console.WriteLine("Therefore, the current week is Week {0} of the current year.", myCal.GetWeekOfYear(DateTime.Now, myCWR, myFirstDOW))  
  
    ' Displays the total number of weeks in the current year.  
    Dim LastDay As DateTime = New System.DateTime(DateTime.Now.Year, 12, 31)  
    Console.WriteLine("There are {0} weeks in the current year ({1}).", myCal.GetWeekOfYear(LastDay, myCWR, myFirstDOW), LastDay.Year)  
  End Sub  

Answer 3

Hi JoseZero-8614.
Firstly may I say sorry for the very late reply.

Secondly I have had trouble with my Computer I had to re-install windows and I have lost everything including databases Programs I had written.
So I am starting afresh with Visual Basic.

Thirdly Thank you for getting back to me on this question.

With the code you kindly posted Does not help me. as I am using Date time picker, textboxes, Labels.

The procedure I am trying to use is....

1. When a user selects a date from a DateTimePicker, The selected date is then inserted into a textbox called (TxtDateFinancialYearStarts)

2) A second DateTimePicker is now use, and when a date selection is made, A Label called (LbWeekNo) gives the current week number.

But When the date has passed one year (Last day of the First Year), I want the Label (LbWeekNo) to reset to week (1) as if a new year has started.
I know some years have 52 weeks and Some years have 53 Weeks (in Financial Years)

The Code I have right now is below...

Private Sub DtpDateFinancialYearStarts_ValueChanged(sender As Object, e As EventArgs) Handles DtpDateFinancialYearStarts_ValueChanged
        TxtDateFinancialYearStarts.Text = GetDateFromString(DtpDateFinancialYearStarts.Text)
        GetWeekNumber()

End Sub

Private Sub GetWeekNumber()

    Dim startDate As Date = GetDateFromString(DtpDateFinancialYearStarts.Text)
    'Dim Day As FirstDayOfWeek = TxtFirstDayOfTheWeek.Text
    Dim newDate As DateTime = Date.Now()
    Dim dateDif As TimeSpan = newDate.Subtract(start Date)
    Dim weekNo As Integer = (dateDif.Days \ 7) + 1
    TxtWeekNumber.Text = weekNo.ToString()

    Dim weekNumber As Integer
    If WeekNumber < 10 Then
        TxtWeekNumber.Text = "0" & weekNo.ToString()
    Else
        TxtWeekNumber.Text = weekNo.ToString()
    End If

End Sub



Function GetDateFromString(s As String) As Date
        Dim d As Date
        If Date.TryParse(s, d) Then Return d
        Return Now
    End Function

Kind Regards
Gary