As a calendar owner or a user with Edit permissions, you can manipulate with events from other sources within your calendar. Navigate to Calendar Settings → Integrations:
Export Calendar to iCal formart
This functionality allows you to get a snapshot of your calendar events in iCal format. This snapshot can be imported to another calendar, for instance, to Google Calendar.
To export the current calendar push the "Export" button. Calendar's issues and events will be downloaded to your computer as an iCal (.ics) file. Following is the example of Calendar events imported to Google Calendar from .ics file:
Import from iCal file
This functionality allows you to upload a snapshot of events exported from another calendar (i. e. Google) to your calendar. Read: Export your Google calendar.
Select the exported file and import it to the calendar. Imported events are added as Non-JIRA Events with default color. Following is the example of the event imported to Calendar:
Google Calendar Sync
This functionality allows you to fetch a single google calendar (public or owned by you) to a particular calendar. Any user with access to the calendar in Jira will see the events that you fetched to this calendar from Google.
The functionality only works if global integration settings are all set, so in case of any troubles contact your Jira Admin.
Firstly, you will need your Google Calendar ID. Follow the steps to find it:
Open your Google Calendar app page using your Google account.
Navigate to your subscribed/available Google calendars list (usually bottom left side).
To get to your calendar settings, hover over the calendar you wish to work on and click the three vertical dots that appear to the right – this will bring up a dropdown menu, click Settings and sharing.
Press the Import button, then in case of a private calendar, you will need to authorize your Google account.