Android Question Cycling through dates

Sub Globals
   Dim lblDate As Label
End Sub

Sub Activity_Create(FirstTime As Boolean)
   lblDate.Initialize("")
   lblDate.Text=DateTime.Date(DateTime.Now)
   Dim btnNext As Button,btnPrevious As Button
   btnNext.Initialize("changeDate")
   btnNext.Text="Next"
   btnPrevious.Initialize("changeDate")
   btnPrevious.Text="Previous"
   Activity.AddView(lblDate,0,0,60%x,15%y)
   Activity.AddView(btnPrevious,0,20%y,30%x,15%y)
   Activity.AddView(btnNext,30%x,20%y,30%x,15%y)
End Sub


Sub changeDate_click
   Dim stepDate As Int
   Dim tempBtn As Button=Sender
   If tempBtn.Text="Next" Then
     stepDate=1
   Else
     stepDate=-1
   End If
   Dim tempDateOfLabel As Long=DateTime.DateParse(lblDate.Text)
   tempDateOfLabel=DateTime.Add(tempDateOfLabel,0,0,stepDate)
   lblDate.Text=DateTime.Date(tempDateOfLabel)
End Sub

Sub btnPrev_Click
    Dim prevDate As String
    Dim totalNoDays As String

    If MasterDay = 0 Then
            t = DateTime.GetDayOfWeek(DateTime.Now)
            totalNoDays = DateTime.GetDayOfYear(DateTime.Now)    
            t = t - 1
           
            For i = 1 To 7
                If i = t Then
                daymark = t
                    Select daymark
                        Case 1
                            lblWeekDay.Text = "Sunday"
                        Case 2
                            lblWeekDay.Text = "Monday"     
                        Case 3
                            lblWeekDay.Text = "Tuesday"
                        Case 4
                            lblWeekDay.Text = "Wednesday"
                        Case 5
                            lblWeekDay.Text = "Thursday"
                        Case 6
                            lblWeekDay.Text = "Friday"
                        Case 7
                            lblWeekDay.Text = "Saturday"               
                    End Select
                    MasterDay = t
                    changeDate
'                    Main.MyDay1 = Main.MyDay1 - 1
'                    DateMinus = DateUtils.SetDate(Main.MyYear, Main.MyMonth, Main.MyDay1)
                    Exit
                End If   
           
            Next
    Else
   
            t = MasterDay
            t = t - 1
            If lblWeekDay.Text = "Sunday" Then
               t = 7
            End If      
               
            For i = 1 To 7
                If i = t Then
                daymark = t
                    Select daymark
                        Case 1
                            lblWeekDay.Text = "Sunday"
                        Case 2
                            lblWeekDay.Text = "Monday"     
                        Case 3
                            lblWeekDay.Text = "Tuesday"
                        Case 4
                            lblWeekDay.Text = "Wednesday"
                        Case 5
                            lblWeekDay.Text = "Thursday"
                        Case 6
                            lblWeekDay.Text = "Friday"
                        Case 7
                            lblWeekDay.Text = "Saturday"               
                    End Select
                    MasterDay = t
                    changeDate
'                    DateMinus = Main.TodaysDate - 1
                    Exit
                End If   
           
            Next       
    End If

Sub Process_Globals
   Private currentDate As Long
End Sub

Sub Globals
   
End Sub

Sub Activity_Create(FirstTime As Boolean)
   If FirstTime Then
     currentDate = DateTime.Now
   End If
   Activity.LoadLayout("1")
   ChangeDays(0)
End Sub

Private Sub btnNext_Click
   ChangeDays(1)
End Sub

Private Sub btnPrev_Click
   ChangeDays(-1)
End Sub

Private Sub ChangeDays(delta As Int)
   Dim p As Period
   p.Days = delta
   currentDate = DateUtils.AddPeriod(currentDate, p)
   Activity.Title = DateUtils.GetDayOfWeekName(currentDate)
End Sub