With the latest iOS 9, there are certain new features that are simply awesome. But there are some features that are creepy or annoying. Almost every stock app on iOS has received some or the other upgrade. Say it Siri or Spotlight; have been enhanced to improve their usability.
Calendar app is no different; managing different events is much easier with the new upgrade. When you receive an email with a specific date in body text, Calendar automatically suggests adding it in event, and by default it adds it to unconfirmed events. This is certainly useful, but many times these are just random dates and seeing this suggestion every time can get annoying.
If you are one of those who likes to manage their stuff on their own, and wish to disable this feature; Apple has given a window to disable it inside Settings app. Just check guide given below to disable suggestion option in Mail app (check this post to disable Calendar event suggestions on Mac).
How to disable suggested event in Calendar in iOS 9 on iPhone/iPad
Step #1. Open Settings app from home screen.
Step #2. Scroll down and tap on Mail, Contacts, Calendars.
Step #3. Scroll down to “Calendars” heading and simply toggle OFF “Events Found in Mail“.
After doing so, you will not receive any suggestion about adding an event to Calendar under Mail app. Also note that if there are any unconfirmed events in Mail app, they will automatically be deleted along with preventing future suggestions.