stackoverflow

 Private Sub tmrNow_Tick(sender As Object, e As EventArgs) Handles tmrNow.Tick
        curT = DateTime.Now
        txtNow.Text = curT.ToString("hh:mm")
        '1st Class
        If curT.Hour = 7 AndAlso (curT.Minute >= 0 And curT.Minute <= 45) Then
            lblPeriod.Text = "1st Period "
            txtPassed.Text = curT.ToString("mm:ss")
            '2nd Class
        ElseIf (curT.Hour = 7 And curT.Minute > 50) Or (curT.Hour = 8 And curT.Minute <= 30) Then
            lblPeriod.Text = "2 nd Period "
            Dim first As DateTime = CDate("07:50")
            Dim second As DateTime = CDate("08:35")
            Dim current As DateTime
            current = DateTime.Now
            Dim diffBefore As TimeSpan = current - first
            Dim diffAfter As TimeSpan = second - current
            txtPassed.Text = diffBefore.ToString("mm\:ss")
            txtLeft.Text = diffAfter.ToString("mm\:ss")
            '3rd Class
        ElseIf (curT.Hour = 8 And curT.Minute > 40) Or (curT.Hour = 9 And curT.Minute <= 25) Then
            lblPeriod.Text = "3 rd Period "
            '4th Class
        ElseIf (curT.Hour = 9 And curT.Minute > 40) Or (curT.Hour = 10 And curT.Minute <= 30) Then
            lblPeriod.Text = "4 th Period "
            '5th Class
        ElseIf (curT.Hour = 10 And curT.Minute > 35) Or (curT.Hour = 11 And curT.Minute <= 20) Then
            lblPeriod.Text = "5 th Period "
            '6th Class
        ElseIf (curT.Hour = 11 And curT.Minute > 25) Or (curT.Hour = 12 And curT.Minute <= 10) Then
            lblPeriod.Text = "6 th Period "
        Else
            lblPeriod.Text = "Free time"
        End If


    End Sub