It is hard to say how much time every person would need, because everyone is different. What is important is that when the person does not have to go back to work right away, they can seek out resources. And those resources can go a long way towards helping the person re-enter the workforce.
The timeframe can certainly vary. One person may be able to deal with the brunt of the shock in a few weeks or months. So the period needs to be long enough to give people the opportunity to put their life back in order and re-integrate into the workforce.