When does the mourning period (iddah) for my mother end, given that her husband passed away on Rabīʿ al-Ākhir 4, 1427 AH, corresponding to May 1, 2006 CE, at approximately 10:00 PM, knowing that the burial took place on May 3, 2006? And is the iddah calculated according to the date of the country where he passed away, or according to the date of our country, which differs by one day?

The 'iddah (waiting period) for a woman whose husband has died begins from the date of his death. It is four months and ten days for a woman who is not pregnant, based on the Almighty's saying: "And those who are taken in death among you and leave wives behind - they, [the wives], shall wait four months and ten [days]." As for the pregnant woman, her 'iddah ends upon delivery of her burden. The difference in date between the place of death and the place of residence has no effect. The 'iddah is reckoned by lunar months, and the month in which the death occurred must be completed to thirty days after the three subsequent months, then ten additional days are added.