CB Subs Calendar Year Plan, Change the calendar year

I have a calendar year plan from 4/1 with grace periods already used. 
The customer wants the plan to go from 6/1 going forward. 
Can I  change the plan year date to 6/1 and make sure the grace period is after the 3/31 expired date will extend the plan to that date?  Then once the time is past, I can go back and adjust the grace period?

Or do I need to create a whole new plan and make that the only upgrade possibility?
Thank you

Depends on if you've recurring payments or not. Recurring payments are locked into the initial configuration. If you're ok with that or don't have recurring payments you can adjust it however you like any time you like.