Oops, it doesn't look like 'uk ceremony for holocaust memorial day' is a national day..

Other days

cursing

Cursing Day

slime

Slime Day

my little pony

My Little Pony Day

lost sock memorial

Lost Sock Memorial Day

Me Day

donate your hair

Donate Your Hair Day

believe

Believe Day

pumpkin

Pumpkin Day

kiss a ginger

Kiss A Ginger Day

carpenters

Carpenters Day