Is this only for good Muslims or for everyone? How about non-Muslims who die on these days? Please list which days, and the corresponding Hadith(s).
The fundamental principle for being saved from any punishment of the hereafter is Imaan. If a person passes away without Imaan, he will be punished irrespective of him passing away on any auspicious day in Islam.
However, if a person passes away Thursday night (after Maghrib) or Friday (till Maghrib) with Imaan, he may be saved from the punishment of the grave due to the auspiciousness of Friday. This is confirmed by a Hadith. It should also be noted that Allah Alone has the right of punishment. He may punish whosoever He wishes and spare whosoever He wishes.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai