Nobody is going to revoke your acceptance for failing to withdraw until the first business day after the recommended date.
"*If any date falls on a weekend/holiday the recommendation(s) will apply to the following business day."
"9. If you receive an offer of acceptance from more than one school or program, choose the school at which you will enroll by April 30. Then, promptly withdraw your application, by written correspondence, from all other schools or programs that have offered you an acceptance."
I've started to withdraw from schools that I would 100% not attend over other acceptances, but you don't have to at all until the date above.