The United Nations began celebrating International Women's Day in 1975, which had been designated International Women's Year, but it was in 1977 that the General Assembly invited member states to designate 8 March as the UN Day for women's rights and world peace.
For some, IWD is a way of celebrating womanhood, but for many it is a protest, to draw attention to the still-ongoing battle by women for equal participation and equal opportunities, in society and in their development as people.
Many of us remember the 1970s as a time when the term "women's lib" was first used, but in fact there were already calls for equal rights for women in the early years of the 20th century, and a 'National Women's Day' was organised by the Socialist Party of America and celebrated in New York on February 28, 1909.
Two years later, on 19 March 1911, the first International Women's Day was marked in Austria, Denmark, Germany and Switzerland, with protesters calling for the right to vote and to hold public office, and against discrimination in employment.
In 1914, Germany celebrated its International Women's Day on 8 March for the first time, and it was dedicated to the right to vote, although German women were not given that right for a further four years. On the same day, in London, there was a march from Bow to Trafalgar Square to call for women's suffrage, and Sylvia Pankhurst was arrested outside Charing Cross Station as she was about to head to Trafalgar Square, where she was due to make a speech.
Other countries decided to follow Germany's example, and mark IWD on 8 March.
In Russia, on that date in 1917, female textile workers in Petrograd held a mass demonstration and women in St Petersburg went on strike for "Bread and Peace", demanding the end of World War I, an end to Russian food shortages, and the end of czarism. Their protests gained massive support and started a revolution; just one week later Nicholas II, the Emperor of Russia, abdicated and the interim government granted women the right to vote.
In some countries, International Women's Day is marked as a public holiday. Spain is not among them, but in 2018 millions of women all over the country went on strike to defend their rights, resulting in schools and universities closing, limited public transport and essential services cut back to a minimum level. Women were also urged not to do housework for 24 hours, and after a social media campaign called 'Take off your aprons' many women hung aprons outside their homes as a sign of support.
Union representatives say about six million women went on strike last year, and similar action is planned today, calling for fair promotions for women, the closure of the gender pay gap and an end to sexual harassment.
There have been advances over the decades, but there is still a long way to go before women receive the necessary support as equal members of society.