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
Just to help people out if they need it:
On the "Code.gs" page, when you follow step 1 and click on the ⓘ, then click the "copy" icon on the top right (looks like two files on top of each other), a new window/tab will open with a Google Apps Scripts project called Copy of GAS-ICS-Sync that you will then customize
On the "Code.gs" page, when you follow step 2, you want to go down to Line 28 of the script code and replace:
icsUrl1
...with the URL of the subscribed calendar that you want Google-Calendar to re-fresh or re-sync with
and also replace:
targetCalendar1
...with the Name of the calendar in Google-Calendar that corresponds to the subscribed calendar
NOTE - I did not type the name of the subscribed calendar exactly the same by mistake, and a new subscribed calendar was created under "My Calendars" that was a duplicate of the previously subscribed calendar under "Other Calendars" - this was no big deal, I just un-ticked the subscribed calendar under "Other calendars" for now (I could remove it completely if I want)
Repeat the above 2 steps if you have additional calendars
Otherwise, you can delete the lines of code that have example text for other calendars
Then follow the rest of the instructions (I left the other lines of code as-is; the info on the "Code.gs" pages explains what all the settings are and you can decide how to set them)
It works for me, and I had never done anything like this before!