I have an application that can be downloaded, registered and then tested for 60 days.
When this time is over the application refuses to work and asks for an unlock code instead.

So far so good.

However a user (not necessarily the most clever one) might come to the idea to set the
system date back, and so get the application back to life.

The question now is, how to track and catch that (betraying) behaviour.

One idea would be to log the date/time upon application start and write this down
at a safe place. Then, if a start-date is before another start date lock the application
(witch again would have to be written to a safe place). Of course there must be
a "time-buffer" to allow normal time-adjustments and summer/winter-time changes.

Nicer would be, if the computer had an internal clock (like You have running hours on
machines) that could be read.


Any other ideas, experiences?

Thanks for any replies