What is the duration of grief or mourning for a death in Islam and when it starts?

If I remember well -correct me if I'm wrong- usually the duration for a the grief or mourning for a death person in Islam is of three days. Now if a Muslim died in a non-Muslim country where the death body is not allowed to be buried unless the legal paperwork is done which takes 1-2 days and then the family must find an adequate graveyard where Muslims are buried. It might already take 3 or 4 days (and even more if the person for example died in the weekend) for all of this ... this made me wonder if the grief or mourning for the wife (wives) and female relatives starts with the death of the person or with the burial? So my question is: How long is the per Islam prescribed grief for a death relative and when does this grief actually starts?