According to mainstream science, the moon gets its light from the sun:
The moon shines because its surface reflects light from the sun. And despite the fact that it sometimes seems to shine very brightly, the moon reflects only between 3 and 12 percent of the sunlight that hits it.
This is a judgment by appearances because the moon also reflects light from the earth:
When you look at a crescent moon shortly after sunset or before sunrise, you can sometimes see not only the bright crescent of the moon, but also the rest of the moon as a dark disk. That pale glow on the unlit part of a crescent moon is light reflected from Earth. It’s called earthshine.1
Light reflected by the moon is always a combination of sun light and earthshine. The amount of earthshine may be negligible to modern science, but Jesus who created all things knows the truth about light from the moon and His description correctly makes this distinction because it differentiates that light from the sunlight:
Mark 13:24 (KJV) But in those days, after that tribulation, the sun shall be darkened, and the moon shall not give her light (φέγγος),
Matthew 24:29 (KJV) Immediately after the tribulation of those days shall the sun be darkened, and the moon shall not give her light (φέγγος) and the stars shall fall from heaven, and the powers of the heavens shall be shaken:
Revelation 22:5 (KJV) And there shall be no night there; and they need no candle, neither light of the sun (φωτὸς); for the Lord God giveth them light: and they shall reign for ever and ever.
The word used for light from the moon, φέγγος is different from φῶς used for light from the sun.
Light from the moon: φέγγος
Light from the sun: φῶς
Jesus is not saying the moon is giving its own light; He is (correctly) stating there is a physical difference between the two types of light.