A period of academic leave generally comprises one full semester. Usually you will have a limit of two consecutive semesters. Overall you can only be “on leave” for the half of the standard period of study (“Regelstudienzeit”) of the relevant course of study (f.ex. within Bachelor programs you can be “on leave” for 3 semesters in total). This limit may be exceeded with one additional semester in justified exceptional cases.
However, leave of absence due to the following reasons: illness, maternity leave, caring for a child younger than four years of age and nursing relatives in need of care is exempt.