detect system date change, visual basics
Dim today As Integer
today = Format(Now, "dd")

Dim iMinute As Integer  'The "current" minute

Private Sub Form_Load()
    'Initialize
    iMinute = Format(Now, "n") 'Get the current time as minute
    Timer1.Interval = 1000 'Set interval = 1000 milliseconds
    Timer1.Enabled = True 'Start Timer1 (my Timer)
End Sub

Private Sub Timer1_Timer()
    'This happens when the given Interval has passed (in this case, every second)
    Dim iMinuteNow As Integer

    iMinuteNow = Format(Now, "n")
    If iMinuteNow <> iMinute Then
        MsgBox "You are now in a new minute"
        iMinute = iMinuteNow
    End If
End Sub