Rotation calculation does stop at 360 degrees

Calcuation in the rotation does stop at 0° or 360° degrees. Like this:

330° + 90° = 420° and does result in 360° which equals to 0° in illustrator.

What I want is the following 

330° + 90° = 420° which should result in 420° - 360° = 60° or

90° - 120° = -50° which should result in 360° - 50° = 310°