next to its name.
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 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, you can refresh a shared calendar, for example in your iCloud account.
Refresh a shared calendar: Shared calendars are updated when the account they’re in, such as iCloud, is updated. To set how often your account is updated, choose Calendar > Preferences, click Accounts, select the account, then click the Refresh Calendars pop-up menu and choose an option. If you choose Push, the account is updated 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 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 calendars: Choose View > Refresh Calendars.
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.