Calendar

Hello Smackie1,

Thank you for using Apple Support Communities. It's my understanding you'd like to retrieve calendar events that were accidentally deleted. My calendar events are extremely important and keep me organized throughout my day. I know how valuable these events can be. I am happy to help.
If you were using iCloud, the calendar events can be restored using the steps and information below.

Several things happen when you restore an earlier version of your calendars and reminders:

• Your sharing settings get erased. You can share the calendars and reminders again, or you can ask the owner to share them again.
• iCloud cancels and recreates all of your upcoming, scheduled events, then resends the invitations for you.

To restore your missing calendars and reminders:

1. Sign in to iCloud.com.
2. Click Settings.
3. Scroll down and click Restore Calendars and Reminders under Advanced.
4. Click Restore next to the date before you deleted your calendars and reminders.
5. Click Restore again to confirm. After the restore completes, you'll get a notification on iCloud.com and an email to the address on file with your Apple ID.

If you accidentally deleted your calendars, reminders, or contacts from iCloud

Also if you have an iTunes backup, the iPhone can be restored from a recent backup. Keep in mind this will remove all recently added content and restore to the content that was available on the date of the backup. Here's some additional information on iTunes backups and how to restore from a backup.

About backups for iOS devices

Restore our iPhone, iPad, or iPod touch from a backup
Have an amazing day!