How many days does your residence permit to be valid when coming back to China?

I am on a residence permit in China which are valid for a year - it ends on the 31st of March. I am flying back to China from Holland on the 29th of March and arriving on the 30th of March. Is there a 'minimum number of days' that my permit needs to be valid before coming back to China or can I access the country without any problems and then start my permit extension process on the 30th?