Oops, it doesn't look like 'gb day' is a national day..

Other days

ruby

Ruby Day
brow

Brow Day
lost sock memorial

Lost Sock Memorial Day
tulip

Tulip Day
self care

Self Care Day
my little pony

My Little Pony Day
hiv awareness

Hiv Awareness Day
lash

Lash Day
cat girl

Cat Girl Day
nae nae

Nae Nae Day