Preferable way would be using Android Calendar Provider (http://developer.android.com/guide/topics/providers/calendar-provider.html). But this API is Java only.
I didnt found anything for the Android NDK Api to access Android Calendar.
Also QT 5 mobile api only lets you access Sensor / Location / Bluetooth and NFC data (http://doc.qt.io/qt-5/mobiledevelopment.html).
Is there any way to query the Android phone calendar from a C++ / QT project?
Edit: I need future appointments the user has in his calendar