When Is National Sis Day?

The internet history of Sis Day

8th of August is National Sis Day

  First detected on the 10th of April 2015

  1,481 tweets


Is It Sis Day Today?

It's Sis day on the 8th of August.

The most recent detection of references to Sis Day was 2 years, 9 months ago.

There were many celebrations relating to national holdiays written about on social media that our algorithms picked up on the 8th of August. In total we detected 97 total unique days being shared such as Sister Day which had 5,274 people talking about it, or Sisters Day having 3,036 tweets.


How Is The Date For Sis Day Calculated?

The day shown for 'National Sis Day' is based off how much chitter-chatter and buzz there was on Aug. 8, 2016 across social media making references to 'Sis Day'. 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, including others such as: Cat, Friendship or Dollar Day. This crowdsourcing of data method to assess the National Sis Day date is used as opposed to being connected with any Government sacntioned lists :D Hurrah for democracy by concensus!


I'd Like To Promote National Sis Day

We've put together the following resources full of nifty tips on how to increase the reach of Sis Day. The resources include: graphs, badges, and resources on what steps to take to boost Sis Day's visibility.

Can I Register Sis Day?

We don't have an international authority or governmental remit to declare any officially celebrated "national Sis day". We only aim to programatically reflect what 'National Day' it is based of what The Internet Says It Is. We believe this is much more fun as it reflects the nature of how the most amusing / interesting national days are often created organically and grow based off popular social trends and sharing, as such we don't add new days to our database unless they are organically observed on social media.



Is it National Sis Day Everywhere?

Yes? No.. Sort of | Maybe ¯\_(ツ)_/¯

What's really intersting is how whilst some National Days like National Daughters Day are seemingly celebrated internationally irrespective of geography, some very popular days (That often become the No. 1 National Day on our homepage) are in fact locally very specific and are offical holidays celebrated on a Country's national calendar. Take National Rambutan Day for instance, Rambutan is a popular Souteast Asian fruit and not seen so much in the UK, Europe or the USA. Some regionally specific trends subsequently become immensely popular internationally and worldwide, partly fuelled by widely shared 'National Days', National Pabebe Wave Day being one such example.


We're now tracking the sentiment around every mention of Sis day to show how people feel about Sis. See if people like Sis here.
We're detecting how Sis affects other things more widely than just being a celebrated day. See how Sis affects company share prices.


Hang On, It Was National Sis Day Already This Year..!?

Yes, this is strangely enough entirely possible. The date shown for National Sis Day can change, if for instance several hundred people tweeted about Sis Day in early April, then in May a few thousand people tweeted about Sis day, then the date shown for National Sis Day, could come up twice :D

We have also detected mentions of Sis day on;



Get The Badge

National Sis Day

It's Sis Day
On August 8th


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National Sis Day, on the 8th of August

Other Days

National Dog Day
National Donut Day
National Puppy Day
National Girlfriend Day
National Best-Friend Day
National Single Day
National Daughter Day
National Boyfriend Day
National Pug Day
National Daughters Day
National Pet Day
National Pancake Day
National Hug Day
National Hot-Dog Day


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For people who wish to promote National Sis Day, we've put together the following resources.
See also: How do Sis affect the share price of Apple, Facebook, Microsoft?
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