Missing iPhone calendar alerts can have frustrating results, especially if it causes you to be late for a crucial event or deadline. There are a few settings on your iPhone, like time zone support and sounds, that can lead to alert issues. In addition, iCloud syncing issues can prevent your phone from receiving updated event listings, and third-party calendar services might have settings that conflict with your iPhone's functionality.

Time Zone Support

Sometimes time zone support can throw off your calendar alerts, especially if it is set to a location other than the one where you are. Open the "Settings" menu, select "Mail, Contacts, Calendars," scroll to the Calendars section, and then tap "Time Zone Support." When this feature is switched on, your iPhone shows calendar events and plays alerts based on the location you select in the Time Zone field. If the time zone location displayed is incorrect, change it by tapping "Time Zone," and then typing in your current city. Alternatively, switch this feature off to have your iPhone automatically use your current location to determine the time.

Sound Settings

Your iPhone might not have a sound assigned to calendar alerts, which can cause you to miss important reminders. Open "Settings," tap "Sounds," and then check the "Ringer and Alerts" volume slider to make sure it is set at an audible level. Keep in mind that calendar alerts do not sound if your phone is set to vibrate. Scroll down to Calendar Alerts, and then select a tone that grabs your attention. In this window, you can also select a custom vibration for your calendar alerts. Make sure to avoid the "None" selection, because this silences your calendar alerts.

iCloud Syncing

Your calendar alerts might not operate properly if your iCloud account is having trouble syncing calendars. Open "Settings," select "iCloud," and then make sure that the username displayed in the Account field is correct. In addition, check to see if "Calendars" is switched on. Tap "Account," type your current iCloud password into the Password field, and then press "Done."

Third-Party Calendar Syncing

Some third-party calendar services, such as Google Calendar, have settings that allow you to control event notifications. These settings might conflict with your iPhone settings, leading to alert issues. Visit your calendar service's website and check to see if alerts are enabled on your account. For Google Calendar, sign in with your Google username and password, open the Settings menu by clicking the icon that looks like a small gear, select "Settings," choose the "Calendars" tab, and then click "Reminders and Notifications." Google allows you to set alerts, such as emails or SMS messages, before an event begins, and these features can provide you with extra alert security.

Version Dislcaimer

Information in this article applies to iPhones running iOS 7. It may differ slightly or significantly with other versions of iOS.