If you can consume an ICS file, you can get the link to one from the Subscribe option in your calendar's '...' menu.
Atlassian documentation on doing this (lists Google Calendars, Outlook, and Apple Calendars as supported but this should work for other clients that can fetch from a .ics): https://confluence.atlassian.com/teamcal/subscribe-to-team-calendars-from-google-calendar-273285887.html
Note that according to the documentation, this is only an option for Confluence Server and won't work with Confluence Cloud.
I beg to differ. We have at least 4 Calendars that we use to subscribe to the team calendars on Confluence Cloud - and it works wonderfully within MS Outlook.
Adding to Daniel's comment above.
There is an issue with ics with Google calendars. It appears to be broken though the calendaring team cannot replicate. https://jira.atlassian.com/browse/CONFSERVER-53690
This may be due to a firewall blocking the Google responses via ics. I do not know. Either way if you are finding google calendaring isn't talking too Confluence calendaring, that is the reason.