Create moths content type with start and end date (calendar field), add a record for each month.
Create
events search type with start and end date fields as search criteria.
If you have only one calendar field for your event, you need to add 2
fields both having the same storage as your existing calendar field, so
that it will only find items from specific month (see this article - http://www.seblod.com/resources/manuals/intermediate/playing-with-match-modes )
Trying to figure out myself. I am also in a similar situation where I am trying to group content types (forms) by a certain field name. The only thing I can think of is using Joomlas default API to query the db for the data you need in your content view.
If your content view has a full_text field you can use an extension such as Regular Labs Sourcerer to write your query and then take your results and style it accordingly: Selecting Data Using JDatabase
I haven't quite worked out the details yet but I know this is probably the best direction
Easiest way to do this would probably be to create new template (based on existing one eg. seb_list, there are no overrides for list tempaltes) and do grouping there