Android Question Adding x amount of minutes to a time held in a label.text field

Sub Activity_Create(FirstTime As Boolean)
    'Do not forget to load the layout file created with the visual designer. For example:
    'Activity.LoadLayout("Layout1")
    Dim timestrold As String = "10:35"
    Log("Time old (String): "&timestrold)
    Log("Time new: "&addminutes(timestrold,7))
End Sub
Sub addminutes(oldtime As String, minutes As Int) As String
    Dim oldtimeformat As String = DateTime.TimeFormat
    'Log(DateTime.DateFormat)
    'Log(DateTime.Date(DateTime.Now))
    'Log(DateTime.TimeFormat)
    'Log(DateTime.Time(DateTime.Now))
    DateTime.TimeFormat = "HH:mm"
    Dim dateold As Long = DateTime.DateTimeParse(DateTime.Date(DateTime.Now),oldtime)
    Dim p As Period
    p.Initialize
    p.Minutes = minutes
    
    Dim datenew As Long = DateUtils.AddPeriod(dateold,p)
    Dim timereturn As String = DateTime.Time(datenew)
    'Log("Time new: "&timereturn)
    DateTime.TimeFormat = oldtimeformat
    Return timereturn
End Sub