Ptuj Castle summer opening hours:

From May 1 to October 15: every day from 9 a.m. to 6 p.m.
Saturdays and Sundays in July and August: from 9 a.m. to 8 p.m.

From April 27 to October 15 2018 the entrance to the lower castle courtyard will be possible till 9 p.m.