Use Case:
User should be able to create a recurring event. Example: every Monday and Wednesday for a month.
Solution:
1) Navigate to the Calendar Gear > Create and Edit
2) Edit your desired calendar and navigate to Create and Edit Popup
3) Here ensure Create Recurring Series of Events is in the selected list of fields. Save, you are now ready to make recurring events.
4) To create a recurring event, click on the appropriate spot on the calendar and select the desired calendar (for which you have executed previous steps). In the create screen, you will now see a dropdown which allows you to specify recurrence. For the example above, we want an event to repeat for a month every Monday and Wednesday. Select the Weekly on Day option.
5) This option will enable several relevant fields (Days of the week selection, recurrence start and end dates) that will help you setup the recurring event. Select appropriate options and Save.
6) Your recurring events should now be created.
NOTE: Recurring events can only be set up against the Event (Activity) Object. Any recurring events created from CA UI in lightning will be created as classic recurring events, this is a Salesforce limitation.