A light-year is a unit of distance, not time. It represents the distance that light travels in one year in the vacuum of space, which is about 5.88 trillion miles (9.46 trillion kilometers). Since light travels at a speed of approximately 186,282 miles per second (299,792 kilometers per second), it takes about 1 year for light to travel this distance.
To convert light-years to "Earthy" years (or any other unit of time), you cannot use a simple formula because light-years and years are measurements of different quantities. However, you can use the speed of light to estimate the time it would take for light to travel a specific distance in years.
To calculate the time it would take for light to travel a given distance in years, you can divide the distance in light-years by the speed of light. The formula would be:
Time (in years) = Distance (in light-years) / Speed of light
For example, if you want to know how many "Earthy" years it would take for light to travel 10 light-years, you would divide 10 by the speed of light. The resulting value would give you an approximation of the time in years.