One gossip website said this "bending" of the rules was done in a bid to "please" Prince Harry because Queen Elizabeth II "might favour Meghan over Kate simply because she's seen evidence of her strong work ethic".
May 19 is a Saturday and the same day as next year's FA Cup final.
The Twitter account of Kensington Palace posted the official announcement of the big date - May 19th, which also happens to be my birthday! Yay!
The Queen and Duke of Edinburgh said they were "delighted" for their grandson and his bride-to-be, and "wish them every happiness".
The wedding will be paid for by the royal family.
A royal wedding has been anticipated since the couple made their first appearance together in September at the Invictus Games, the prince's sporting tournament for injured or sick veterans.
Prince Harry's older brother, William, the Duke of Cambridge, who is President of the Football Association, usually attends the match and presents the trophy. The couple met in a little over a year ago, thanks to their friends who introduced them.
We're so excited for the couple.
Ms Markle, a protestant, will be baptised and confirmed before the wedding, the palace added.
The pair became engaged in London earlier this month, and modern man Harry sought the blessing of both of Ms Markle's parents.
It is not yet known if the ceremony will be conducted by the Archbishop of Canterbury.
The Suits actress has been invited to the official royal celebrations at the stately home this year, after announcing their engagement on November 27.
The "Suits" actress will be spending the holidays with the royals and many understand that picking the best gift for the monarch might be hard for Markle.