When do time tampering checks occur?

I use verified trials and standard activations. I also use TurboFloat versions of the program. Would the only time that the time tampering checks occur be when I call TurboActivate.IsDateValid? Or would the time tampering checks occur on IsGenuine or IsGenuineEx as well? How about Activate()? I just need to be able to display good error messages to the user, and would like to take this potential issue into account.

IsGenuine(), IsGenuineEx(), IsActivated(), IsDateValid(), Activate(), ActivateEx(), ActivateFromFile() all do time tampering checks.