When does the 'iddah (waiting period) for the wife of the deceased end, given that he passed away on 24/8/2021?

The 'iddah (waiting period) for a pregnant widow ends upon childbirth. For a non-pregnant widow, her 'iddah is four months and ten days. The 'iddah is calculated using lunar months. If your father passed away on August 24, 2021 (which was Muharram 16, 1443 AH), then her 'iddah would end on Jumada al-Ula 24, or Jumada al-Ula 25 if Muharram had 29 days. The calculation of the 'iddah begins from the moment of the husband's death.