As seen in the New York Times, whatnationaldayisit.com is the largest datasource of national days on the internet. We automatically include popular holidays from what is being referenced across social media using data-mining and natural text analysis to work out which national days have the highest significance.
It's worth mentioning that the national days shown are according to 'the internet' and this site makes no claims as to any 'officially' sanctioned national day, governmental or otherwise.
Note people on the internet can say mean things :/ The days shown on WNDII aren't filtered for sensitivity of language as an accurate display of current talking points is the intention here, EG 'According to the internet, apparently it's National Spork Day'... This can mean that rude or mean days can sometimes be reflected on the site. If you do see anything offensive, please do get in touch and request it's removal.