Donald Trump posted a picture of his own inauguration with a huge mistake printed onto it.

The President posted on Twitter a picture of a "photo delivered yesterday that will be displayed in the upper/lower press hall," he wrote alongside the picture. He thanked its photographer, Abbas Shirmohammadi.

But the picture's inscription includes a huge mistake. Written at the bottom is a date – "January 21st, 2017" – which is actually the day after Mr Trump was inaugurated.

The swearing-in ceremony that the picture depicts actually happened on 20 January, a day that Mr Trump has officially declared to be the "National Day of Patriotic Devotion".

January 21 was actually the date of the anti-Trump Women's March around the world, which was according to some estimates far better attended that Mr Trump's inauguration and was the biggest day of protests in US history.

The error may be the result of the photographer using the same date as Barack Obama's inauguration in 2013. That took place on 21 January and a picture on Mr Shirmohammadi's website shows an almost identical picture with the same caption.

Trump Inauguration protests around the World Show all 14 1 /14 Trump Inauguration protests around the World Trump Inauguration protests around the World Activists from Greenpeace display a message reading "Mr President, walls divide. Build Bridges!" along the Berlin wall in Berlin on January 20, 2017 to coincide with the inauguration of Donald Trump as the 45th president of the United State Getty Trump Inauguration protests around the World An activist holds up a sign at the "We Stand United" rally on the eve of US President-elect Donald Trump's inauguration outside Trump International Hotel and Tower in New York on January 19, 2017 in New York Getty Trump Inauguration protests around the World Protesters burn a U.S. flag and a mock flag with pictures of U.S. President-elect Donald Trump outside the U.S. embassy in metro Manila, Philippines Getty Trump Inauguration protests around the World Filipino protestors hold placcards during a protest rally in front of the US embassy in Manila, Philippines, 20 January 2017. On the eve of President-elect Donald Trump's inaguration as the 45th president of the United States, Filipinos and Fil-Americans held a protest in front of the US embassy in Manila to denounce the incoming US president. Getty Trump Inauguration protests around the World Hong Kong police officers and security guards look on as an anarchist protester belonging to the Disrupt J20 movement sits after using a heavy duty D-lock and motorcycle lock to chain himself to a railing at the entrance gate to the Consulate General of the United States of America in Hong Kong to protest the inauguration of United States President-elect Donald Trump, Hong Kong, China, 20 January 2017. Two activists were arrested and taken away by Hong Kong police during the demonstration. Getty Trump Inauguration protests around the World A banner is unfurled on London's Tower Bridge, organised by Bridges Not Walls - a partnership between grassroots activists and campaigners working on a range of issues, formed in the wake of Donald Trump's election, which aims to build bridges to a world free from hatred and oppression. Getty Trump Inauguration protests around the World Protesters chain themselves to an entry point prior at the inauguration of U.S. President-elect Donald Trump in Washington, DC, U.S. Getty Trump Inauguration protests around the World Bridges Not Walls banner dropped from Molenbeek bridge in Brussels, Belgium, 20 January 2017, in an Greenpeace action part of protests Wolrd protest in solidarity with people in the US, the day Donald Trump sworn in as the 45th President of the United States. Getty Trump Inauguration protests around the World A woman holds an anti-U.S. President-elect Donald Trump placard during a rally in Tokyo, Japan, Getty Trump Inauguration protests around the World A Palestinian protester holds a placard during a demonstration against the construction of Jewish settlements in the occupied West Bank and against US President-elect Donald Trump, on January 20, 2017, near the settlement of Maale Adumim, east of Jerusalem Getty Trump Inauguration protests around the World Banners on North Bridge in Edinburgh as part of the Bridges Not Walls protest against US President Donald Trump on the day of his inauguration Getty Trump Inauguration protests around the World Russian artist Vasily Slonov (L) and his assistant carry a life-sized cutout, which is an artwork created by Slonov and titled "Siberian Inauguration", before its presentation on the occasion of the inauguration of U.S. President-elect Donald Trump, in a street in Krasnoyarsk, Russia Getty Trump Inauguration protests around the World A woman holds a banner during a march to thank outgoing President Barack Obama and reject US President-elect Donald Trump before his inauguration at a park in Tokyo, Japan, 20 January 2017. EPA Trump Inauguration protests around the World Palestinian demonstrators protesting this week against a promise by Donald Trump to re-locate the US embassy to Jerusalem Reuters

Inaugurations always take place on 20 January, unless that date falls on a Sunday. That happened in 2013 and so Mr Obama took the oath privately on 20 January and then did it again at a private ceremony the following day.

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Mr Trump was presumably posting the picture in part because it showed a huge crowd attending his inauguration. The Trump presidency has repeatedly looked to dispute the number of people who turned up to the event – with press secretary Sean Spicer arguing that an optical illusion had led people to be tricked into believing fewer people turned up than actually did.