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
https://script.google.com/home/projects/1BOk8MDLbLaHh6SwG1M1tsgNXjkcC-79LE0QoipRuTDxbO3fMVvqoROQD/edit
This is fantastic, thanks! One change to Settings would be nice:
var onlyFutureEvents = true;
// If you turn this to "true", past events will not be synced (this will also removed past events from the target calendar if removeEventsFromCalendar is true)
It would be nice to have onlyFutreEvents true to make the sync faster, but also leave removeEventFromCalendar also true so any future events that are deleted get removed, but past events aren't touched.