Appointments +: time difference between table and form


I'm using Appointments+ 1.9.4 on my (test)website. Wordpress is set to time zone Brussels.
When I want to create an appointment and I select a time slot starting at 9h00, the confirmation form gives me 8h00. Why is there a time difference? This difference is even 2 hours when there is no daylight saving time.

Please help me fix this issue.