9 a.m. The NY/NJ Trail Conference will host a cleaning and maintenance day on the trails around Alley Pond Park in Queens in honor of National Trails Day.
11 a.m. The Freecycle NYC Spring Cleaning FreeMeet, in which citizens can exchange free new and used goods, will take place at the Harlem YMCA, 180 West 135th Street.
6 p.m. Brooklyn45, a weekly public television program, will host a fundraising dinner in the Banquet Hall at Miller Evangelical Church, 1110 President Street between Rogers and Bedford Avenues, in Brooklyn.
7:30 p.m. Joe Biden, Christopher Dodd, John Edwards, Hillary Clinton and Bill Richardson will appear at the Iowa Democratic Party’s 8th Annual Hall of Fame Celebration Reception and Dinner, airing live on C-SPAN.
11 a.m. New York State Senate Democratic Leader Malcolm A. Smith will be joined by elected officials, environmentalists, health advocates, and community leaders to announce new legislation that would prohibit the use of tetrachloroethylene in New York State. Known as PERC, a synthetic organic chemical commonly used by dry cleaning and auto body businesses, the chemical can be dangerous to humans and animals. This legislation is largely due to the recent discovery of the PERC water contamination in Southeast Queens. Smith will make the announcement at his District Office, 205-19 Linden Boulevard, in St. Albans, New York.
11 a.m. Bellevue South Community Council Festival will be held on Second Avenue between 23rd and 34th streets.
7 p.m. The Democratic presidential candidates will debate in New Hampshire at an event sponsored by WMUR-TV, the New Hampshire Union-Leader and CNN.
10 a.m. The Council Committee on Public Safety will host a hearing to address what NYPD can do to meet its stated goals for hiring and retaining new officers at City Hall.