it is the distance light travels in i year,
According to wikepedia
A light-year is equal to:
* exactly 9,460,730,472,580.8 km (about 10 Pm)
* about 5,878,630,000,000 miles
* about 63,241.1 astronomical units
* about 0.306601 parsecs
The figures above are based on a Julian year (not Gregorian year) of exactly 365.25 days (each of exactly 86,400 SI seconds, totalling 31,557,600 seconds) and a defined speed of light of 299,792,458 m/s, both included in the IAU (1976) System of Astronomical Constants, used since 1984. The DE405 value of the astronomical unit, 149,597,870,691 m, is used for the light-year in astronomical units and parsecs.
The light-month does not have a precise definition or value, as there is no unique definition of a month in astronomical or SI units: however it may be understood to be approximately one-twelfth of a light-year, in line with the various mundane definitions of the month (hollow month, average Julian month, etc.).