The University of Basel distinguishes between two procedures for enrolling in the specialized Master's program Data Science:

New application 
For a new application at the University of Basel, students must register online via the University of Basel website.

Registration deadline for the fall semester is April 30.
Registration deadline for the spring semester is November 30.

Change of degree level, program or subject
Students who are already matriculated at the University of Basel apply for a change to the Master's program with the re-registration via the Online Services. In addition, students must fill out the form Application for Admission to the Specialized Master's Program and submit it in writing (by e-mail via www.unibas.ch/studseksupport or by mail) to the Student Administration Office together with the enclosures mentioned and the supplementary sheet printed out from the Online Services. The form can be downloaded on the Student Administration Office website.

The registration deadline for the fall and also the spring semester is always the end of the re-registration period.