This application was developed to be used without a Facebook account.
Therefore it does not use the Facebook API. Instead it opens the Facebook event URI and downloads the website source code. This source contains the information which is used to create a calendar entry.
This Android app is written in Java and is using the Gradle build system. To compile it, i recommend using Android Studio.
I develop this application in my free time. If you like it, you can donate at PayPal.