It was the queen’s birthday Thursday, but only one of them.

“The official birthday is in June,” explained Geoff Donovan.

“I thought this was the official birthday,” said his friend John Colemon-Woods.

“No, this is the actual.”

“Oh, right.”

The pair, retired veterans who served in Korea, had come to Hyde Park to watch the British cavalry mark the event with 40 exceedingly loud cannons.

“What they did was, back when there was some king, his birthday was too cold and rainy,” Donovan continued. “So they moved it.”

A Buckingham Palace official confirms this: The king was Edward VII, November-born, and during his reign he decided to celebrate a second birthday in June and coordinate it with the Trooping the Color, an elaborate military parade.

Now all kings and queens officially have June birthdays, even if their birthdays are, for instance, April 21. At least in Britain — the queen has different official birthdays elsewhere in the Commonwealth. In Australia, it is timed to the opening of ski season to provide a three-day weekend.

In the United States, many roving birthdays are celebrated: Christopher Columbus’s, George Washington’s — all of which provide Mondays off to the working public. Of course, the original celebrators are dead. There is something either very egotistical or very modest for a living person to say, “Let’s just ignore the calendar, shall we, and do it when it’s nice out?”

The actual queen celebrated her actual 85th birthday participating in Maundy Thursday services at Westminster Abbey, where a highly excitable crowd clustered as if in some mini-quake dress rehearsal for the royal wedding.

“It’s only the Duke of Wellington!” shouted a tall man with a good vantage point as a town car pulls in front of the abbey. (“Only a duke,” everyone passed down.)

Finally, the queen’s maroon Rolls-Royce pulled up to the abbey, and the queen alighted with her husband, Prince Philip, the Duke of Edinburgh. She was wearing a robin’s-egg blue dress, with a matching hat, as is her wont, and she smiled briefly at the crowd before going in.

“So you’ve seen the queen?” a frazzled-looking mother asked her two children. “So you’ve seen her?”

The boys nodded that they had seen the queen.

“Good. Then let’s go get some lunch.”