iPhone Calendar Events Disappear? How to Restore Calendars on iPhone

Q: All my calendar data is deleted like hospital appointments, meetings with friends and reminders, etc. It is disastrous because I even don't know if I have an event tomorrow. How can I restore my calendar data from iPhone in the most stress-free method?
A: There are various reasons why old Calendar events disappeared or got lost on iPhone/iPad, such as iOS upgrade, wrong sync settings, accidental deletion or shared Calendar information with others. Don't fret! It is fairly simple to fix for disappearing calendar events as well as to recover deleted calendars from iPhone/iPad with iPhone Recovery software.

Syncing the old events

The settings for the Calendar app might get reset when you upgrade or restore or reset your iDevice. And this might prevent older events from syncing back to the calendar app. To fix this, here's what you need to do.

First, confirm that you've turned on iCloud Calendar by tapping Settings > iCloud on your iPhone or iPad, then check that Calendars is turned on. 
If you have synced your iPhone with another calendar service, the iDevice may automatically deletes old events. Then you need to change the sync settings for your calendars:

1. Tap Settings > Mail, Contacts, Calendars.
2. Scroll down to Calendars, tap Sync. If Sync is set to All Events, set it to a specific duration, such as Events 1 Month Back. If it's already set to a specific duration, set it to All Events.
3. Tap the Home button. Wait several minutes, then open Calendar and try to refresh your calendars again.

Restore lost Calendars from iCloud

iCloud now regularly archives a list of data for both Calendar and Reminders, which provides users with a convenient way to restore deleted or lost calendar events from iCloud.

1. Sign in to iCloud.com and click on the Settings.
2. Under the Advanced section and select "Restore Calendars and Reminders" option.
3. Select the latest archive of calendars and reminders to restore.

Recover deleted Calendar events with iPhone Recovery Freeware

If you accidentally deleted the appointments on calendars without syncing or backup, you're advised to stop using the calendar app and try Free iPhone Data Recovery to retrieve deleted or lost calendar information/events from iPhone, iPad or iPod touch directly.

 
1. Launch the Calendar Recovery freeware on your computer; Select Calendar and go to the next.
2. Connect your iPhone/iPad to PC; Start scanning Calendar data from your device.
3. Preview and choose the deleted Calendar events to recover.

Youtube tutorial: Restore Lost Calendar on iPhone/iPad