Let's look at how you can solve your problem with ldid. First, you dump entitlements with
ldid -e MobileCal > entitlements.xml
Then you edit dumped entitlements and resign the app binary with
ldid -Sentitlements.xml MobileCal
(Yes, there is no space between -S and entitlement file).
It doesn't work?
helloworldMoblie:~ root# ldid -Sentitlements.xml MobileCal
./minimal/mapping.h(54): _assert(false); errno=2