I'm writing a routine that does some cleanup whenever it senses a change in
the date.  The only way to test my code is to set the date back to
yesterday at 11:59pm and observe the change as it occurs.

I did so, and noticed an error.  So I altered my code to allow for the
error and rolled the clock back a minute or two, so that it was back to
11:59 yesterday.  The same behavior occured.

So I put a MsgBox in the routine to alert me to what the value was for a
couple of variables, and I re-ran the app.  The MsgBox never ran.

I moved the MsgBox to the very beginning of the routine.  Still it wouldn't
fire.

I moved the MsgBox to the first line of the button event that fires the
routine.  Still the MsgBox wouldn't fire.

I removed the MsgBox line, and added Exit Sub to the very beginning of the
button event.  The button still called the routine.

I removed the Exit Sub line, and added MsgBox("loaded") to Form_Load.  The
MsgBox never fired.

I reset the time to the current time and compiled, and everything worked
fine.

It seems as though .NET has some safeguard to keep you from compiling over
a newer version with an older version.  Am I correct in this assumption?