Terminate thread execution for 24 hours - vb.net

Question

I have my service working mostly as it should, but it should only do it's work once every day.
To arrange this, my boss recommended I sleep the worker thread until 7am tomorrow:
This Thread.Sleep call is copied directly from a similar service he wrote that apparently works, but this always throws an ArgumentOutOfRangeException - the value returned is a negative.
Private Sub startExport()
#If Not Debug Then
Thread.Sleep(1000 * 60 * 1)
#End If
While runReportExport
Try
runExport()
Catch ex As Exception
el.WriteEntry("Error exporting data: {1}")
Finally
'sleep thread until tomorrow 7am
Thread.Sleep(DateTime.Now.Subtract(Date.Today.AddDays(1).AddHours(7)))
End Try
End While
End Sub
I'm fairly confused about how this all works so if anyone can explain the whole timespan thing for me, I'd greatly appreciate it.
On the other hand, my friend recommends I manage the thread execution in a different way.
Here's what He recommended I do:
Private lastExecute As DateTime = DateTime.Now
Private Overrides Sub OnStart(ByVal args() As String)
startService()
End Sub
Private Sub startService()
Dim nextExecute = lastExecute.AddDays(1)
If nextExecute >= DateTime.Now Then
lastExecute = DateTime.Now
tWorker = New Thread(AddressOf startExport)
tWorker.IsBackground = True
tWorker.Start()
End If
End Sub
He said this would execute the worker thread once on startup and not again for another day. While this code does work without error, it doesn't stop the service loop from executing the worker thread over and over again (currently it executes a 2nd time as soon as it finished it's first run)
Personally I'm open to either approach, I can't seem to get either working.
Basically, all I need at the end of the day is a service that exports data once daily.
My boss' Thread.Sleep option seems the simpler, but my friend's suggestion seems like better practice.
Can anyone help me to get this sorted (at this point I don't care which one I use, just so long as it works)?

Answer 1

DateTime.Now.Subtract(Date.Today.AddDays(1).AddHours(7)))
You subtract a future time from the current time. That always produces a negative value. Kaboom.
You'll need to invert that, subtracting the current time from the future time. Spelled out for clarity and avoiding the race on DateTime.Now :
Dim today = DateTime.Now
Dim tomorrow = today.Date.AddDays(1).AddHours(7)
Dim wait = tomorrow - today
Thread.Sleep(wait)
You will need to do something useful when the service is stopped. Best done with a ManualResetEvent, you'll get the sleep from its WaitOne(wait) method. Btw, extremely wasteful to have a thread sleep for that long and not doing anything useful. Use a Timer instead.

Answer 2

Another approach, and one I use, to run a specific task once a day is to set the task up in a timer. In my case I want the task to run at 12:05am each morning. Accordingly, when my program starts I set the initial interval of the timer such that the first tick will happen at 12:05 am the next day. After that, once a day, at the end of the code the executed as part of the tick I once again reset the timer interval such that the next tick will happen at 12:05am the next day.
...
Timer1.Interval = MillisecondsToMidnight() + 300000 ' next tick 12:05:00 tomorrow
...
Private Function MillisecondsToMidnight() As Integer
Dim ReturnValue As Integer
Dim ts As TimeSpan
Dim Tomorrow As DateTime = Today.AddDays(1)
ts = Tomorrow.Subtract(Now)
ReturnValue = ts.TotalMilliseconds()
ts = Nothing
Return ReturnValue
End Function