a light year is a unit of distance not time
1 light year = 9.4605284 × 10^15 meters 1 light-second = 299,792,458 meters <-- EXACTLY 1 light year ÷ 1 light second = 31556925.9747 So 1 light year = 1 light second * 31556925.9747 If you want to know how to get these #'s
By defintion a light year is the DISTANCE light travels in one year. So we can write S = CT where S is distance, C is light speed, and T is time. When T = 1 year, we have S = CT = C*1 = 299E6*1*365.25*24*3600 = 9.43572E+15 m as one-light year. Note that T had to be converted into seconds to be consistent with C in m/s. So the 9.43572E+15 is the distance in meters traveled in a year's worth of seconds.
