There's an approx travel time of about 1 hour and 17 minutes
From NEW CANAAN STATION take the STAMFORD STATION bound Metro-North Train.
Transfer to the GRAND CENTRAL TERMINAL STATION BOUND Metro-North Train.
Than you have arrived at GRAND CENTRAL TERMINAL STATION in NYC.
Use the TripPlanner MTA website, it helps you plan your commutes. http://www.mta.info/
The LIRR (Long Island Rail Road) has a train stop in Cold Spring Harbor. The express train goes to Penn Station in about 50 minutes. If you have to drive to Manhattan rush hour mornings about 1hour 15minutes to midtown.