Weekly Gym schedule / irregular recurring Events / D7
Try this: 


Create content types gym1, gym2, gym3... > add suitable fields to them eg. Title and time(name the time field to field_gym1_calendar, reason for this -- see part five).
Create content: EXAMPLE: "content type: gym 3 --> Title: bodypump, Time: 10/10/2013 14:00-14:30".
You can also add a taxonomy "bodypump, zumba, etc..." and add a 'Term Reference'-field to your content type (This way admin doesn't have to type 'bodypump' or 'zumba' every time he's adding stuff to calendar, just select the right one from dropdown-box)
Install "Date Tools" and "Date"- modules
Go to Views > look for button "+ Add view from template" On top of the page.
Search for the NAME of the TIME field you added to CONTENT TYPE gym1.
Should look something like this: "A calendar view of the 'field_gym1_calendar' field in the 'node' base table."
Name this view to 'Gym 1 calendar'- for example.
If you have content in "gym1/......." It should be listed in "Preview" Below


Play around with "+ Add view from template" button, it creates a calendar view of any node type with -date / time- field in it (I think)

All this works in a commerce_kickstart install I'm currently f*cking with.. All the modules you need are listed in my comment... don't know. Have fun :)