Hëävÿ Mëtäl Ümläüt Däÿ is typically celebrated in newspapers, and on various internet forums on July 29th each year. It is typically celebrated in
, in small towns where people are eccentric but just don't know it. It's a fairly obscure holiday, popular to polygamists and to members of the Obscure Holiday Practicing Society, and unpopular to pretty much everyone else. The day has absolutely no affiliation to Heavy Metal Day (February 11th, official day to celebrate the lower left half of the periodic table, which feels like it never gets enough attention). Utah
On Hëävÿ Mëtäl Ümläüt Däÿ, which also has no affiliation to heavy metal, or to umlauts, one is dedicated to the usage of unnecessary foreign diacritical marks in as many words as one could get away with, without coming off like they're trying too hard.
(More specific rituals could be traced back to the Hëävÿ Mëtäl Ümläüt Däÿ chapter in the Book of Extremely Unecessary Religious Rituals)