How long does it take to get from New York to China?

Answer 1

A direct flight from New York to Beijing takes about 13 hours and half (flights operated by Air China and Continental).
China is a big country, so it defers if you are going to other cities. To Shanghai, for example, there are no direct non-stop flights. United operates flights through Chicago, which take about 19 hours.
These and other routes are also served by connecting flights.

Answer 2

Depends on which New York and / or which city in New York.

Depends on where in China you are travelling.

Depends on how you choose to travel to China.