On the day the wireless network crashed, Mr. de Blasio was in Nevada, an early primary state, as he considered whether to declare his candidacy for president. City Hall initially tried to hide the shutdown. It made no public acknowledgment of the problem and, in response to questions from The New York Times, officials initially characterized it as a routine maintenance issue.

The report does not indicate when Mr. de Blasio was told of the problem or whether he was informed of the confusion surrounding the attempts to get it working again.

In a statement accompanying the report’s release, Laura Anglin, the deputy mayor for operations, who also oversees the information technology department, asserted that “there were no interruptions to city services during the NYCWiN outage,” but acknowledged that “it is critical we learn from this event.”

Ms. Anglin’s statement, however, is directly contradicted by the report, which details several service interruptions. About half of the city-operated signs showing arrival times at bus stops were disabled, as were about 200 cameras that provide online images of traffic conditions; many other tasks handled by the network were knocked offline, requiring city workers to be reassigned to perform the tasks manually.

The report made it clear the episode could easily have been avoided. The wireless network, like many other computerized systems, uses GPS data to keep track of time. The GPS rollover was widely known, and government and industry notices encouraged technology managers to upgrade systems to avoid possible interruptions.

The report’s authors interviewed eight top officials at the information technology department, including Mr. Saini. But the report said that no one at the agency admitted being aware of the approaching rollover. It does not say whether it considered those denials to be credible, given the amount of publicity related to the rollover in the technology industry.

Mr. Saini was hired just a year and a half ago by the mayor and was involved, among other key initiatives, in the modernization of the 911 system. Attempts to reach Mr. Saini were unsuccessful.