Yes, sign in at www.ontutor.net and click the [Edit my Tutor Profile] button on the right, and edit the available hours on the [Set Availability] tab.

It is possible to set regular hours, such as "every Monday from 5:00 pm to 6:00 pm" as well as a one-time period.

However, those courses the students have already registered for cannot be changed, as those students registered

for the courses based on the information you've given before. You will need to teach the course as agreed, or

contact the student directly for other changes.