Oops, it doesn't look like 'cathedral becomes a mosque for a day' is a national day..

Other days

healing

Healing Day
raise awerness of zeus

Raise Awerness Of Zeus Day
ask out your crush

Ask Out Your Crush Day
believe

Believe Day
my little pony

My Little Pony Day
promposal

Promposal Day
self appreciation

Self Appreciation Day
cursing

Cursing Day
donate your hair

Donate Your Hair Day
self care

Self Care Day