This Wednesday on January 9, Duchess Catherine will ring in her 37th birthday.
There's no doubt the mother-of-three will be surrounded by her nearest and dearest including children Prince George, five, Princess Charlotte, three, and youngest son Prince Louis, eight months.
But it appears there'll be one key person missing for part of the celebrations - her husband, Prince William.
This will be the first time in six years the royal couple have spent some of her birthday apart as it's been confirmed by Kensington Palace the Duke of Cambridge, 36, has already committed to an official engagement at the Royal London Hospital in east London for an event for the 30th anniversary of London's Air Ambulance on the same day as Kate's birthday.
"The Duke of Cambridge will visit @LDNairamb on Wednesday 9th January to recognise the work that their first responders carry out delivering life-saving treatment across London," the palace's official tweet explained.
Indeed, the air ambulance holds a special place in William's heart after he worked for the service for two years from 2015-2017.
The devoted father also worked as a search and rescue pilot for five years with the RAF.
While duty may call, Kate will also be busy as this week marks the return of school after the Christmas break for Prince George.
Kensington Palace declined to comment over Kate's birthday plans, only revealing she will be spending the day "privately."
Last year, Kate, who was heavily pregnant with Louis at the time, reportedly celebrated with a "small birthday party of eight" at Kensington Palace.
"But she is not drinking any alcohol and she is being careful with her food too," an insider told the Daily Star Online at the time.
It's believed the VIPs who landed a coveted invite to the intimate bash include Wills and Kate's good mates Guy Pelly and his wife Elizabeth Wilson.
Kate's BFF and Princess Charlotte's godmother Sophie Carter was apparently also there, and it's believed her sister Pippa Middleton and brother James Matthews popped by.