Here are some pointers if you like to join us as a student, PhD student, postdoc, or guest. Vacancies are advertised at the university's general page, and sometimes also on this page. However, most PhD and postdoc positions are not formally advertised, but awarded year round based on individual applications.
Being a PhD student in Leiden means having a paid job for four years. There are usually vacancies on externally funded research projects. There may also be positions funded by the Mathematical Institute. If you are interested, the best strategy is to contact a professor who is specialised in your field of interest.
For general information on PhD positions in Leiden, consult http://www.universiteitleiden.nl/en/science/graduate-school-of-science/ You can start at any time of the year.
Postdocs and guests
If you are interested in a postdoc or guest position please contact a professor in your field directly.