DateTime.Parse-fejl

Hejsa!

Jeg får ved denne linje kode
if (DateTime.Now.Ticks >= DateTime.Parse("634421553176875000").Date.AddDays(-14).Ticks)
følgende fejl:

System.FormatException was unhandled
  Message="String was not recognized as a valid DateTime."
  Source="mscorlib"
  StackTrace:
      at System.DateTimeParse.Parse(String s, DateTimeFormatInfo dtfi, DateTimeStyles styles)
      at System.DateTime.Parse(String s)
      at ToDo.Data.UpdateNotes() in C:\Documents and Settings\Toke\Dokumenter\[PRIVAT]\C#\ToDo\ToDo\Data.cs:line 41
      at ToDo.Form_Main.MainForm_Load(Object sender, EventArgs e) in C:\Documents and Settings\Toke\Dokumenter\[PRIVAT]\C#\ToDo\ToDo\Form_Main.cs:line 22
      at System.Windows.Forms.Form.OnLoad(EventArgs e)
      at System.Windows.Forms.Form.OnCreateControl()
      at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)
      at System.Windows.Forms.Control.CreateControl()
      at System.Windows.Forms.Control.WmShowWindow(Message& m)
      at System.Windows.Forms.Control.WndProc(Message& m)
      at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
      at System.Windows.Forms.ContainerControl.WndProc(Message& m)
      at System.Windows.Forms.Form.WmShowWindow(Message& m)
      at System.Windows.Forms.Form.WndProc(Message& m)
      at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
      at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
      at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
      at System.Windows.Forms.SafeNativeMethods.ShowWindow(HandleRef hWnd, Int32 nCmdShow)
      at System.Windows.Forms.Control.SetVisibleCore(Boolean value)
      at System.Windows.Forms.Form.SetVisibleCore(Boolean value)
      at System.Windows.Forms.Control.set_Visible(Boolean value)
      at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
      at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
      at System.Windows.Forms.Application.Run(Form mainForm)
      at ToDo.Program.Main() in C:\Documents and Settings\Toke\Dokumenter\[PRIVAT]\C#\ToDo\ToDo\Program.cs:line 18
      at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
      at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
      at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
      at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
      at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
      at System.Threading.ThreadHelper.ThreadStart()
  InnerException:

Altså: Den kan ikke parse "634421553176875000". Hvorfor ikke?