The problem has raised questions about whether the city had taken appropriate measures to prepare the network for the GPS rollover.

Ms. Raphael did not respond to questions about what the city had done to prepare for the rollover; she said that the city pays $37 million a year to Northrop Grumman to maintain and operate NYCWiN. A Northrop Grumman spokesman referred all questions to the city.

“If the city’s paying $40 million a year to maintain software infrastructure, first, when it goes down, the Council and the public should know about it,” said Councilman Brad Lander of Brooklyn, who learned about the shutdown when he was told of it by The New York Times.

“And two, if it’s mission critical, then it should be clear: the effort to get it up and running, and account for those things that are lost.”

Mr. Lander, who sits on the City Council’s technology committee, said that the committee might hold a hearing to look into the cause of the shutdown and how it was handled.

Many computerized systems use the Global Positioning System as a timekeeper because it is convenient and easy to connect to, according to a Department of Homeland Security advisory about the reset posted on the agency’s website.

Approximately every 20 years, the GPS needs to reset the way it keeps track of weeks, and Saturday, April 6, was the date selected for the most recent reset. The reset also came with an improvement in timekeeping that means the next rollover will not be needed for about 157 years.