Keep track of events in Calendar on iPhone
In the Calendar app , you can customize the notifications that let you know about upcoming Calendar events, invitations, and more. You can also make sure your events and other calendar information are kept up to date on all your devices.
Customize Calendar notifications
Go to Settings > Notifications > Calendar.
Turn on Allow Notifications.
Tap a type of event (for example, Upcoming Events), then choose how and where you want the notifications for those events to appear—for example, on the Lock screen, in Notification Center, as banners at the top of the screen, with an alert sound, and so on.
Keep your Calendar up to date across your devices
You can use iCloud to keep your Calendar information up to date on all your devices where you’re signed in with the same Apple ID.
Go to Settings > [your name] > iCloud, then turn on Calendar.
If you don’t want to use iCloud for your Calendar, you can sync your Calendar information between your iPhone and your computer. See Sync iPhone with your computer.