Given a subscribed calendar with a url like
https://example.com/example.ics
To force Google Calendar to refresh and reload the contents right now, unsubscribe from the calendar and subscribe to a new calendar with a URL like
https://example.com/example.ics#1
Adding the anchor tag will force Google Calendar to think of it as a new calendar
Many people who come to this gist are not looking for a one time forced refresh but instead to refresh recurringly. If that's you, you should check out @derekantrican 's Google App Script
https://github.com/derekantrican/GAS-ICS-Sync
Which can refresh a calendar automatically every N minutes
Thanks to @rattrayalex for pointing people to this script
I finally got this working and it’s great! I wanted to post a mistake I was making in case it helps anyone out in the future. It seems like a simple mistake but took me a few days to figure out.
I created a calendar in Google from an iCloud url called “Appointments.” It was a read-only calendar. When I added in my source url and target calendar on code.gs line 28, nothing worked. I thought I was inputting the wrong url.
After searching the boards, I realized I needed to create a new calendar in Google and delete the read-only calendar. I called the new calendar “Appointments” as well. I put in my source url and the target calendar (Appointments) and everything worked. Hope this makes sense and I hope it helps.