They have an answer for (almost) everything.

Whether it’s the writers of “Mad Men” calling to ensure the hit show’s portrayal of the city in 1963 is accurate, or a fourth-grader stumped on her science project, the research librarians at the New York Public Library are the question authorities.

Created in the 1960s as the telephone reference desk, the team of six senior librarians in the catalogue area of the stunning Rose Reading Room now take hundreds of questions each day by phone, e-mail, online chat — and, as of a few weeks ago — by text message.

Most of the requests relate to mundane matters such as obtaining a library card, but each day there are several dozen juicy “cherry questions,” senior librarian Bernard van Maarseveen told The Post.

“These are our bread-and-butter questions — the ones that keep us coming in each day and keep us from calling out sick,” he said. “These could take days or weeks.”

The writers of “Mad Men,” for instance, call frequently while working on the show. For example:

“Right now on taxi cabs you have lights that say ‘off duty,’ and they wanted to know if those lights were on in 1963,” said Maarseveen, whose desk is piled with books filled with such Big Apple arcana.

“They also wanted to know what was scheduled to be on TV the day of the Kennedy assassination,” he said.

Some of the questions are beyond the reach of Google, which often generates more results than answers, said Samantha Thompson, who manages ASK NYPL.

“We’re there for those times when what you find on the Internet is insufficient,” she said.

The librarians are sometimes referees as well as references.

“A golfer called to settle an argument — for which there was clearly money on the line,” Thompson said. “He asked what is the rule if a bird picks up a golf ball and moves it off the green.”

After consulting the game’s rule books, she settled their bet. “As long as it’s not a trained animal, moving the ball counts as a hazard of the course.”

There are some questions the librarians will not answer.

“No personal questions such as ‘What are you wearing?’ — which we do get,” Thompson said. “We also don’t answer medical or legal questions — although we will point you to a resource.”

Although the librarians often do information grunt work for academics and novelists, they draw the line at children’s homework.

The free service is available 24 hours a day, with a consortium of librarians as far afield as Australia picking up the slack during off hours.

While 90 percent of the text-message questions have been pretty basic, some have been genuinely thought-provoking, Thompson said.

“My favorite so far was: ‘What would happen if the moon exploded?’ ” she said. “That needed some clarification. He meant, if the moon were to disappear, would the lack of reflected light on earth cause the planet to freeze?”

The answer, she texted back, is no. “The tides would be a problem though,” she said, “It would not be good for surfers.”

jeremy.olshan@nypost.com

