Two application clocks run in parallel: a general one for most programmes, and a much earlier, unforgiving one for numerus fixus places. Applicants abroad also have visa steps and diploma recognition queued up behind the Studielink registration, so a deadline that looks comfortable in November rarely is.
Studielink is the national portal every prospective student uses to register for a Dutch degree programme and, if eligible, request DUO student funding — it runs alongside applying to the university or hogeschool (university of applied sciences) itself, though in practice the two happen together. For programmes with unlimited places, the standard deadline is 1 May before the September start. Numerus fixus programmes (medicine, several psychology tracks, physiotherapy at some institutions) run on an earlier, stricter clock: you need to be fully registered in Studielink by 15 January, with no late applications accepted after that. The selection procedure then runs from 16 January to roughly mid-April, with results out by 15 April; if you're offered a place you typically get about two weeks to accept before it passes to the next candidate. You can apply to at most two numerus fixus programmes per academic year. If you're coming from outside the Netherlands and need extra time for visa steps or diploma recognition, start well before 15 January regardless — Studielink doesn't extend the deadline for paperwork still in progress elsewhere. Selection weighting (grades, motivation letter, sometimes a test) varies by programme even within numerus fixus, so check the specific programme page rather than assuming one process fits all.