With MyShiftPlanner Pro, you can use the Multiple Patterns feature to change your rota but keep your old shifts in the calendar.
-Tap on the COG
-Tap Patterns
-Tap Start a new rota+
-Select your new rota and add start date after your current rota.
-Hit Next and Save your rota to your calendar.
-You’ll now see two rotas, one Current and one for the future.