As with any other situation where an employee leaves with procedures being followed( period of notice etc.) then that is the agreed date of termination. In a position of good employer employee relationships it is natural for the employee to feel guilt at leaving and an obligation to lessen the problems this may cause the employer.
It is the employers responsibility that all required duties eg, documentation hand over etc are completed by the date of termination and the employees to facilitate this. The appointment of your successor is the total the employers responsibility and how they meet this is down to them. There is no hard and fast laid down procedures and PC's are no different from any other employer.