King Charles III's coronation will take place on the same day his grandson Archie turns four years old.
It's the second time this year a royal event has clashed with a birthday for Harry and Meghan's children.
Lilibet turned one on June 4 during Queen Elizabeth's Platinum Jubilee weekend. A small garden party was held at Frogmore Cottage for the auspicious occasion, where the Queen was reported to have met Lilibet for the first time.
Buckingham Palace confirmed on Wednesday morning the King's coronation will take place at Westminster Abbey on May 6 (local time).
The date was chosen in consultation with the UK government, the Church of England and the Royal Household.
"The ceremony will see His Majesty King Charles III crowned alongside The Queen Consort," a palace statement said.
"The coronation will reflect the monarch’s role today and look towards the future, while being rooted in longstanding traditions and pageantry."
It will be the first coronation of a British monarch in nearly 70 years. At the time of her death, Queen Elizabeth was one of the longest-reigning monarchs in history - she became Queen in 1952 and was coronated in 1953. Her eldest son Charles, 73, was the longest-serving heir apparent in British history.
Royal historian Marlene Koenig told Hello magazine it seemed unlikely that Harry and Meghan would be attending the event in May.
"Archie is too young to attend the coronation. But Charles was four-and-a-half. However, Archie is not heir to the throne or even remotely close to the throne."
The ceremony itself has already come under intense scrutiny, with plenty of changes marked for the event which was last held in 1953.
According to reports, Charles' coronation will be cut from three hours to just over one hour. The guest list will go from 8000 people to just 2000 with many missing out on the day itself, which is due to see a more relaxed dress code rather than traditional ceremonial robes.
Ancient and time-consuming rituals - including presenting the monarch with gold ingots - will also be axed to save time.
It's been confirmed there won't be an official public holiday in recognition of Charles' coronation, like the one observed in September to commemorate the Queen following her death.
"We won't be making the coronation a public holiday in New Zealand. May 6 falls on a Sunday our time, which means there's an opportunity for many people to watch the coronation and mark this special occasion in other ways too if they wish to," a spokesperson for the Prime Minister said.