In order for classes to show in the Classes drop-down on a users My Day, the academic term that the course is offered in needs to be current. 

To determine the Academic Term:
  1. Go to the Core persona.
  2. Navigate to Settings > School Information > Years & Terms
  3. From the Selected Year drop-down, select the appropriate school year.
  4. Select the appropriate School Level from the drop-down.
Here you will find any academic terms for the school year, as well as the start and end dates. The start and end dates determine when the class appears in the Classes drop-down.