On my S3 I was able to disable S Planner and just use Google Calendar. HD Widgets would then launch Google Calendar rather than S Planner because that was the only calendar left on my phone after S Planner was disabled.
However on my new S5, there are two instances of S Planner in Application Manager and I can only disable one and not the other. HD Widgets keeps launching S Planner over Google Calendar because that's the "favourite" or "default" calendar.
Anyone successfully disable these built in apps on the S5?