When does the 'iddah (waiting period) end for a wife whose husband died on February 6, 2018, and whose 'iddah began on February 7, knowing that she is elderly and has ceased menstruating?

The waiting period (iddah (definition)) for a widow begins from the time of her husband's death and lasts for four months and ten days, unless the wife is pregnant, in which case her iddah ends upon childbirth. The iddah is calculated using lunar months. If the husband died on the 19th of Jumada al-Awwal, and the month had thirty days, then she observes iddah for 12 days of Jumada al-Awwal, then Jumada al-Akhirah (definition), Rajab, and Sha'ban, and her iddah ends on the 28th of Ramadan (definition) at the same time of death.