Oops, it doesn't look like 'anthem at brexit day' is a national day..

Other days

ruby

Ruby Day
reading

Reading Day
martini

Martini Day
donate your hair

Donate Your Hair Day
nae nae

Nae Nae Day
believe

Believe Day
carpenters

Carpenters Day
boy friend

Boy Friend Day
tulip

Tulip Day
aloxolt

Aloxolt Day