Further investigation showed that since iOS 10 Apple requires to provide reasoning whenever you are using sensitive data in which NSCalendar is included.
TelerikUI provides an easy way for the TKCalendar to get synchronized with the device's calendar and that specific action is though of as information sensitive.
Unfortunately we weren't able to find a way to resolve the issue globally, for example, by adding the NSCalendarsUsageDescription variable to the info.plist of the framework.
Bottom line you should try adding NSCalendarsUsageDescription variable to your app's info.plist and provide a description like "This app need to access your calendar events", it will be prompted to the user only if there is an attempt for actually retrieving the calendar events information, meaning that if you do not use this feature your users will never get that prompt.
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