Oops, it doesn't look like 'flags at wembley day' is a national day..

Other days

self care

Self Care Day
bow tie

Bow Tie Day
pampering

Pampering Day
youth

Youth Day
emoji

Emoji Day
bonang

Bonang Day
brow

Brow Day
slime

Slime Day
my little pony

My Little Pony Day
boy friend

Boy Friend Day