Ruth Freitag, Librarian to the Stars, Dies at 96

“These bibliographies would take months and even years to do,” said Jennifer Harbster, head of the science reference section at the Library of Congress. “It wasn’t like you just found a title and put it in your bibliography. She would annotate it all.”

She also compiled bibliographies on general-interest topics, including presidential inaugurations and whether a new decade or century is considered to begin in the year ending in zero or the year ending in 1. Ms. Freitag, along with other authoritative sources, firmly believed that they begin on the 1 — that the 21st century, for example, started in 2001, not 2000, despite the many celebrations to the contrary.

As the third millennium loomed, she assembled a pamphlet, “Battle of the Centuries” (1995), with lively quotations about the dispute over the ages.

“Bibliographic work may sound dull at first,” she told an internal Library of Congress publication, The Gazette, in 1990, “but it can really grow on you, to the extent of becoming a vice.”

Ms. Freitag spoke several languages and knew all the proper accents to place on words — “all the unusual ones for whatever language she was writing in,” said Brenda Corbin, the former head librarian at the Naval Observatory. When computers first came along, Ms. Corbin said, Ms. Freitag “wasn’t happy” that they didn’t have accent marks, which meant that she couldn’t write correctly. “She was meticulous.”

Ms. Freitag often helped researchers with their writing.

“She was one hell of a copy editor,” said Mark Littmann, the former longtime director of the Hansen Planetarium in Salt Lake City, who researched some of his popular astronomy works (including “Planets Beyond” and “Totality: Eclipses of the Sun”) at the Library of Congress.