alfiomantineo,
I have been trying to replicate what you describe but so far it has been working correctly. There were some resent changes to the code that calculates the days remaining.
Try updating the program as described on the wiki:
http://rayshobby.net/mediawiki/index.php?title=Python_Interval_Program_for_OSPi#Updating_the_program
and let me know if you still see the problem.
Dan