“This law is now in its 51st year, and it needs to reflect that.”

The biggest change to the Landmarks Law would be to add timelines for public review of potential landmark buildings and historic districts. Under the proposed bill, individual properties would have to be approved within a year of being suggested for landmark status, while historic districts, which can include hundreds of properties, would have a two-year deadline.

Since 1998, according to the Council’s report, 82 percent of individual landmarks were considered within one year, while 86 percent of historic districts were voted on in two years. There is presently no deadline, and dozens of properties had been under consideration for decades before the commission cleared the backlog this year.

“What I’ve discovered, calling around to my colleagues around the country, is that lots of historic commissions have some kind of deadlines,” said Peg Breen, president of the Landmarks Conservancy, an advocacy group.

Others still worry.

“This bill remains ill advised,” Tara Kelly, the director of preservation and design at the Municipal Art Society of New York, said in an email. “The timeline for historic districts is too short; MAS holds fast to our position that three years is more appropriate.”

In a concession to preservationists, the bill includes the elimination of a previously proposed five-year moratorium on the ability to reconsider properties that do not receive landmark status.

Councilman Greenfield said the timeline bill had 30 co-sponsors, giving it a good chance of passing the 51-member body. And while Mayor Bill de Blasio’s administration previously opposed the stricter rules, it has now given the bill its tacit support.