Company Changing Bonus Payable Date

Hey y'all, recently I've got a thought in my mind.
Let's say company A announced that they're distributing bonus on Dec 10th, and they stipulated that you've got to be an employee of the company at the date to receive the bonus.(固定賞与)

Then, employee A tenders his resignation, with his last day on Dec 10th.

If the company changes the date of bonus distribution by 1 day to Dec the 11th, will that be allowed?
This is a pretty small company where the director knows every employee working in the company.

Thank you!

by supermegadeth