When neutrinos are propagating in the ordinary matter, the coherent forward scattering of neutrinos off the background particles may significantly affect neutrino flavor conversions. In this talk, we investigate the matter effects on solar neutrinos when they traverse the Moon during the solar eclipses. A comparison with the day-night asymmetry of solar neutrinos, which has been measured to be about 3% in the Super-Kamiokande experiment, is also made.