How to calculate the warranty period of Party B's recruitment?

According to relevant information, the warranty period shall be calculated from the date when the referee officially starts to work for Party A, and the warranty period for senior or technical employees recommended by headhunting companies is 3 months. During the warranty period, if a new employee resigns voluntarily or passively for personal reasons, the headhunting company will replace it or refund the headhunting fee according to the agreed proportion.