You may wish to set up appointment slots for your students or advisees. Moodle has a Scheduler activity that allows you to create repeated slots within a time frame (for example, Monday, Wednesday, and Friday of a particular week from 1:30 to 3:30 PM), and students can select a particular slot to reserve that appointment online. You can set up an option to remind the student of the appointment (via email), and students can change their booking if their plans change.
Here are detailed instructions on how to add a Scheduler to your Moodle course and configure its options. The instructions describe how to do that for your "Advisor" course in Moodle, but those instructions apply as well to any of your Moodle courses.