Filtering by date

At this point ICS Calendar just pulls in calendar feeds and formats them for display. It doesn’t retain any event data in any kind of a database structure where this kind of advanced processing across the data loaded by different shortcodes could be done.

The closest it could come, and you may need to tinker with it a bit, would be to set up another page with a single shortcode that contains all of the feeds. (A shortcode can contain multiple URLs in the url parameter, separated by spaces or pipe characters, and the events from those will get consolidated into one displayed calendar.)

You may want to try that as a starting point, and then experiment to see if you can get it to display what you want. Depending on how heavily you want to get into the code, there are some hooks you can use to do additional processing of your own on the parsed data:

https://icscalendar.com/user-guide/#developer

I think the r34ics_display_calendar_filter_ics_data filter would probably be the most useful in this case. To start, you’d probably want to do a var_dump() on $ics_data to see the array structure.