To add a Google calendar to Jira with the Calendar for Jira plugin, you will need to follow these steps:

  1. Install the Calendar for Jira plugin from the Atlassian Marketplace.

  2. Once the plugin is installed, go to the calendar page in your Jira instance and click on the "Add Calendar" button.

  3. In the "Add Calendar" dialog, select the "Add calendar subscription" option.

  4. Enter the name and URL of the google calendar (2nd part of this doc), and then click the "Create" button.

You should now see your Google calendar events in the calendar view in Jira. You can also use the Calendar for Jira plugin to create events in your Google calendar from within Jira.

To get the public iCal URL for a Google calendar, follow these steps:

  1. Go to your Google calendar.

  2. Click on the calendar you want to get the iCal URL for.

  3. Click the "More" button (the three vertical dots) in the top right corner of the calendar.

  4. Select "Settings and sharing" from the menu.

  5. Scroll down to the "Integrate calendar" section.

  6. Click on the "Public address in iCal format" link to get the iCal URL for the calendar.

You can then use this iCal URL to access the calendar from other calendar applications that support the iCal format, for example, Calendar for Jira.

Note: The iCal URL for a Google calendar is not the same as the URL for the calendar's page on the Google Calendar website. The iCal URL is specifically for importing the calendar into other applications.