April 21 first
The custom among many Ashkenazim is to pronounce the first two words of Kaddish as "Yitgadel Ve'yitkadesh." This follows the ruling of the Mishna Berura, who maintained that these words are Hebrew, not Aramaic, such that they should be pronounced "Yitgadel Ve'yitkadesh," with the Sereh vowel underneath the Dalet in both words.
However, Rav Meir Mazuz (1945-2025) noted that in ancient sources, these words appear in the Aramaic form – "Yitgadal Ve'yitkadash," with a Patah vowel, and so this is the proper pronunciation. This is, indeed, the custom among Sepharadim.
When reciting the word "Yitgadal," one must ensure to pronounce the Gimmel properly, and not as a Kuf, as though reciting "Yitkadal," a word that means something very different from "Yitgadal." Furthermore, one must make a point to pronounce the Dalet properly, so the word does not sound like "Yitkatal," with a Tav.