Hey Sunset,

I've checked your site and found that this issue is coming for 1 plan only.
this: https://sunsetbeachpilates.com/administrator/index.php?option=com_payplans&view=plan&layout=form&id=1

The reason for the issue is somehow the date was saved incorrectly, I've fixed this issue at your site and now this issue no longer showing your site. There is no error while creating a plan.

Please take a look at this issue again and update us if the still issue persists.

Thank you!