It's a birthday fit for a new king in NSW

The public holiday is celebrated on the second Monday of June even though it doesn't align with either of the monarchs' actual birthdays.

Employee Relations Minister Damien Tudehope said it was important to recognise Australia's new king.

"Most people have only known this public holiday as the Queen's Birthday holiday for every year of the late Queen Elizabeth's 70-year reign," Mr Tudehope said.

"It is with a touch of sadness that we must move to change the name, but it is an important recognition of the new monarch, King Charles III, that the public holiday will continue and be henceforth named the King's Birthday public holiday."

The late Elizabeth II's actual birthday was April 21 while King Charles's is November 14.

Britain officially celebrated the event in June because of the greater chance of fine weather.

The first King's Birthday public holiday will be on June 12, 2023.