San Diego’s mayor, Bob Filner, besieged by reports of sexual misconduct with several women, resigned at 5 p.m. on a Friday in August. The principal of Stuyvesant High School, under the cloud of a cheating scandal, and the president of St. John’s University, dealing with a financial scandal and the suicide of an assistant dean on trial for corruption, each resigned on a Friday.

After the financial markets close on Fridays has been a time for companies to release potentially damaging financial news, such as of a merger or poor quarterly results. “That is a practice at least as old as the wise men following the star to Bethlehem,” Michael Tobman, a political consultant in Brooklyn, said.

Before the Internet explosion, it was easier for politicians to release controversial news on a day when the next morning’s newspaper might go unread or be used in fireplaces. On Christmas Eve 1992, President George Bush pardoned former Defense Secretary Caspar W. Weinberger and five other people involved in the Iran-contra scandal in the Reagan administration.