A change in how local homes are listed for sale has drawn the ire of some buyers' agents, who say the switch skews information and favors sellers.

Metropolitan Regional Information Systems, which manages a database for 60,000 real estate professionals in the Washington area and parts of West Virginia and Pennsylvania, is changing an element of its "days on market" listing for homes.

It involves decreasing from 180 to 90 the number of days a property is required to be off the market before MRIS resets that number to zero when it gets back on an active listing for "days on market."

In short, it makes it look like homes that have been lagging on the market for several months haven't been out there that long, said Stephen Israel, president of Buyer's Edge, a Bethesda real estate firm that only represents homebuyers, not sellers.

"It's absolutely a knee-jerk reaction to the market," Israel said. "It's great for the seller who can't sell their house, they get a clean slate in 90 days instead of 180. This information won't be directly available to the consumer, only through a broker who goes the extra mile to access the information."

MRIS officials said the move is simply part of an ongoing policy review. The 180-day timeframe was selected in 1993 as an arbitrary figure, and the 90-day timeframe is more appropriate -- market statistics are often generated quarterly, and economists and other market hawks base their observations on quarterly time periods.

"This is more reasonable," said Mary Jo Powell, a spokeswoman for Rockville-based MRIS. "We don't feel it will affect the market any more than it will when the market turns around."

Other multiple listing services, Powell said, have varying rules for "days on market." Philadelphia's service keeps a 30-day timeframe for being off the market before returning to listings, and Minneapolis' is one year, she said.