Question

One light-year is equivalent to how long in time?

Answer 1

Hint: The distance light moves in one second, or \[7.5\] times the distance across Earth's equator, is a light-second. In one year, a light-year is the time light travels. How long has it been? Multiply the number of seconds in a year by the number of miles or kilometers traveled by light in a second, and you've got it there: a light-year.

Complete answer:
In one year, a light-year is nothing but the distance that the light passes. The value is very immense. That's why we use it as a guide, especially in space, to measure distance.
In fact, we use the light-year and not light seconds or light minutes.
Instead of saying 1 minute, it's like saying 60 seconds have gone. Instead of saying 1 year, will you say..... \[31557600\] seconds?
The distance traveled by the light within \[365.25\] days is one light year. Accordingly, \[365.25\]days is \[1year\] , \[1day = 24hours\] ,
\[1hour = 60minutes\] ,
\[1minute = 60seconds\] .
Thus, $365.25 \times 24 \times 60 \times 60 = 31557600 seconds.$
We know that,${{distance = velocity \times time}}.$
where $c = 299792458m/s.$ (speed of light).
Hence 1 light year = $299792458 \times 31557600.$
Which would be, $9.4607304725808 \times {10}^{15}.$
Approximately we can conclude that \[{\text{1 light year}}\] is \[9.4607 \,{\text{trillion km}}\].

Note: Light year is now used for calculating distances to add to your point (though the term is misleading). In this word, the YEAR shows the year of the Earth and not the year of any other planet. For a layman, this seems odd, but "light year" is not a unit of time. Hence, comparing it to a year makes no sense. Kilometers or miles should be contrasted with that. It is a distance unit, a ruler for measuring distances in a vacuum. It is the distance traveled by light, in \[1year\], the quickest thing known in space. And that is a mind bogglingly enormous distance.