How is the waiting period (iddah) calculated for a woman whose husband has died: is it by Hijri months, Gregorian months, or by days, noting that the death occurred on 26 Ramadan 1432 AH?

The 'iddah (definition) (waiting period) for widowhood is specific to the wife whose husband has passed away. It consists of refraining from adornment and waiting to remarry. If she is pregnant, her 'iddah ends upon delivering her entire pregnancy, as Allah Almighty says: "And for those who are pregnant, their term is until they deliver their burdens." (Quran 65:4). If she is not pregnant, her 'iddah is four months and ten days, as Allah Almighty says: "And those of you who die and leave wives behind - they, [the wives], shall wait four months and ten [days]." (Quran 2:234). The 'iddah begins from the time of death and is calculated by lunar months, with the obligation to complete the month of death to thirty days if the death occurred during the month. Accordingly, your mother-in-law will observe her 'iddah for the remainder of Ramadan (definition), and for Shawwal, Dhul-Qa'dah, Dhul-Hijjah, and Muharram. Her 'iddah will end on the sixth of Safar 1433 AH if Ramadan was thirty days, or on the seventh of Safar if Ramadan was twenty-nine days, at the same hour her husband passed away.