On your iPhone or iPad, open Settings
Tap Calendar
Tap Accounts
Tap Add Account
Tap Google
Sign in with your Google account
Turn on Calendars
Tap Save
On your Mac, open System Settings
Click Internet Accounts
Click Add Account
Select Google
Sign in with your Google account
Make sure Calendars is enabled
Open the Apple Calendar app
Wait for your Google calendars to appear
Check the calendar list to confirm the sync
On the web, open Google Calendar
Click the gear icon
Click Settings
Select the calendar you want to sync
Copy the Secret address in iCal format if needed for subscription
In Apple Calendar, choose File
Click New Calendar Subscription
Paste the iCal link
Click Subscribe
To refresh sync on iPhone or iPad, go to Settings
Tap Calendar
Tap Accounts
Tap Fetch New Data
Enable Push or set Fetch to a shorter interval
To refresh sync on Mac, open Calendar
Choose Calendar
Click Accounts
Make sure Google account syncing is active
If events do not appear, confirm the Google account is still signed in
Make sure Calendars is turned on for the Google account
Check that the correct Google calendar is selected in Apple Calendar
Remove and re-add the Google account if needed