One day Ganesha was invited to a feast. Being very fond of sweets, he consumed a large number of sweets. While returning home his stomach burst open, due to the weight of the food consumed. Luckily it was night. Hoping no one had seen him; he quickly tied his stomach with a snake. Unfortunately the moon saw him and burst into peals of laughter.
Ganesha was furious and uttered a curse that the moon would be invisible from then on. The moon was ashamed of his action and begged forgiveness. Ganesha also felt he had been hasty in cursing the moon. But since he could not take back his curse but only lessen it's intensity, he proclaimed that the moon would wax and wane and would be invisible on only one day of the month, " amavasya ", which is, to this day considered inauspicious.