How accurate is the moon phase calculation?

The moon illumination is accurate enough for a normal user. Sometimes, the scrolling bottom line that reports when to expect the full moon may seem to be inaccurate.

For example, lets say that the full moon is for June,14 at 00:20. If you run the screensaver at June 13, 21:00, it will say "full moon tonight" because when we say "tonight" we mean until the dawn. So the program may seem to be inaccurate because technically, 00:20 is "tomorrow".

Disclaimer:
Keep in mind that no guaranty is given that the program can report the moon phase without errors or with a specific accuracy. Users should NOT rely on the program's calculations to preceed to actions that depend on the accuracy of the moon phases.