Refresh calendars
If you publish or share calendars, you may want to refresh them so that others can see your latest changes. Or, if you subscribe to calendars, you may want to check for updates periodically to be sure you have the latest information.
A published, shared, or subscribed calendar has a Share Calendar button 
next to its name.
Refresh calendars
Choose View > Refresh Calendars.
Refresh a subscribed calendar
To automatically retrieve updates, Control-click the calendar’s name, then choose Get Info. Click the Auto-refresh pop-up menu, then choose an option.
Refresh shared calendars in an account
Choose Calendar > Preferences, click Accounts, then select the account. Click the Refresh Calendars pop-up menu, then choose an option. If you choose Push, the account is updated automatically when you make a change on any of your devices that use the same account, or when someone makes a change to a shared calendar in that account.
Refresh a calendar you publish
Control-click a calendar below On My Mac in the calendar list, then choose Get Info. Select “Publish changes automatically.”
If you don’t see the calendar list on the left, choose View > Show Calendar List. If your calendar list doesn’t have an On My Mac section, your calendars are in an account, such as iCloud.
If you see a warning symbol 
next to a calendar you published, shared, or subscribed to, Calendar is unable to connect to the calendar account. Check your Internet connection and try refreshing or updating the calendar again.
Also, make sure the calendar hasn’t been deleted or moved. To see the calendar’s web address, Control-click the calendar’s name, then choose Get Info.