Preparations in London have begun for the birth of Kate Middleton and Prince William’s second child. As previously reported, parking restrictions have already been put in place surrounding St. Mary’s Hospital in Paddington, west London. The streets are blocked off for a “special event” until April 30 – which means that the royal baby could share a birthday with his or her great-grandmother, Queen Elizabeth II.

The Duchess of Cambridge is set to return to the hospital’s Lido Wing, the same location she gave birth to her first child, Prince George, on July 22, 2013. While no official due date has been announced, Kate reportedly told a volunteer at the Brookhill Children’s Center that she was due in “mid-April to the end of April.” Based on the royal baby’s speculated due date, he or she could be born on April 21, Her Majesty the Queen’s birthday.

Queen Elizabeth was born April 21, 1926, the elder daughter of the Duke of York (later King George VI) and his wife, Elizabeth Bowes-Lyon. She was proclaimed queen upon the death of her father on Feb. 6, 1952. Her June 2, 1953, coronation became the first Westminster Abbey ceremony to be televised.

What some don’t know is that the queen celebrates two birthdays every year. According to the British Monarchy site, she spends her real April 21 birthday privately. But the government celebrates her “official” birthday on a Saturday in June. The reason for the second date is “good weather” for the Trooping the Colour/ Birthday Parade celebration, a tradition that began in the early eighteenth century. But that doesn’t mean her actual birthday goes unnoticed. The royal site notes there is a gun salute in central London at midday on April 21.

Queen Elizabeth’s birthday is not the only special occasion the royal baby’s birth could fall on. Prince William and Kate Middleton were married at Westminster Abbey on April 29. This year marks their fourth wedding anniversary.