The speed of light is not infinitely quick, so light that leaves the Sun takes just over 8 minutes to reach us. Sunlight reflecting off the Moon takes just over a second to reach us.
Light from Proxima Centauri, the neareast star to us (other than the Sun) takes over 4 years! We say that Proxima Centauri is just over 4 light years away.
A light year is a unit not of TIME, but of DISTANCE.
1 light year = distance travelled by light in 1 year