My father passed away on April 3, 2021 daytime, 7 th day of Pesach. He was buried on April 5th, 2021. When do I stop saying Kaddish as this is a leap year.

ב"ה Shalom, First of all my condolences to you. May Hashem comfort you among the rest of mourners of Tzion and Yerushalayim. Your father passed away on the 21st of the Hebrew month on Nissan, and the burial took place on the 23rd of Nissan. The Ashkenazi custom is that the Kaddish is said for 11 months from the date of burial which means that you stop saying Kaddish on the 22 of the Hebrew month of Adar I, which comes out this year (2022), on February 23. Although, it is 13 month leap year, according to the Jewish calendar, nonetheless, the Kaddish is said for the same duration of 11 months. However, the Yahrzeit is the day of his death, 21st of the Hebrew month on Nissan, which this year will come out on April 22, even though the year of Avelut= mourning will end a month earlier due to the Hebrew calendar leap year. May you know of no more sorrow. All the best