Monday 9 November marks the day when women working full-time essentially stop earning and work for free the rest of the year, the UK's leading gender equality charity announced today.
Women are paid on average 14.2% less an hour than men according to the Fawcett Society, which analysed 2014 data on the average full-time hourly earnings for men and women using the latest figures from the Office for National Statistics.
After subtracting the percentage difference of average earnings from 100%, the findings revealed women are paid on average 14.2% less an hour than men.
Equal Pay Day was then calculated by subtracting 14.2% of the year (52 days) from the end of the year, producing today's date.
The gender pay gap has declined by 1.3% in the last five years. At this rate of progress, it will take over 50 years to close the gap, the charity claims.
"Progress has stalled in recent years but with real commitment from government and employers, together with action from women and men at work, we could speed up progress towards the day when we can consign it to history," Sam Smethers, the Fawcett Society's chief executive, said in a statement.
Earlier this year, prime minister David Cameron pledged to "end the gender pay gap in a generation". The Conservative government made it mandatory for large companies to publish information about the gender differences in average earnings.
The government claims the national living wage of £7.20 per hour will also help with the pay gap.
The national Trade Union Centre (TUC) has called for the government to go even further by forcing large companies to also publish details of how they aim to solve the gender pay gap within their organisation, as well as fining companies who fail to comply.
Analysis by the TUC released on Monday found that the gap in annual salaries between top-earning women and top-earning men is roughly 55%. The report also shows that some progress has been made in terms of increasing the number of women members on company boards.
Despite this, the annual salary gap for women and men in the top 10% of earners rises as you climb higher up the ladder, with women in the top 2% earning £40,000 a year less than their male counterparts.
Leader of the Women's Equality party Sophie Walker has called for a new, integrated approach to bridging the gender pay gap in order to put an end to marking this "depressing day" every year.
In a statement Walker said: "Forty-five years after equal pay became a legal requirement, we're still waiting for it to become a reality."
The Fawcett Society encouraged both men and women to "talk about pay".
"How can we achieve pay equality if we don't even know what our colleagues earn?" Smethers said. "It is time to have the conversation and ask your employer if they are ready for the new pay gap reporting requirements."
Fiona Rutherford is a reporter for BuzzFeed News and is based in London.
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