This paper presents an innovative approach to curriculum-based timetabling. To capture complex relations of real life curriculum-based timetabling problems, curricula are defined by a rich model that includes optional courses and course groups among which students are expected to take a subset of courses. In addition, courses may contain alternative course sections. A transformation between the proposed curriculum model and student course enrollments is formalized and a local search algorithm generating corresponding enrollments is introduced. While the proposed curriculum model is too complicated for existing curriculum-based solvers, the transformation enables curriculum-based timetabling in any existing enrollment-based course timetabling solver. The approach was implemented in a well established enrollment-based course timetabling system UniTime. The system has been successfully applied in practice at the Faculty of Education at Masaryk University for about 7,500 students and 260 curricula and at the Faculty of Sports Studies at Masaryk University for about 1,400 students and 25 curricula. Experimental results related with these problems are demonstrated for two semesters.