It's National App Day on December 11th.
More on App Day and the other days on the 11th below.
The day shown for 'National App Day' is shown as we detected that day mentioned the most out of all the references to national days there were on December the 11th across social media. Our algorithms examine all of the references to National Days across social media and updates whatnationaldayisit.com hourly, with our homepage displaying the current national day. This crowdsourcing of data method to assess the National Day date is used as opposed to being connected with any Government sacntioned lists :D Hurrah for democracy by concensus!