The legend of king Daksha’s curse on Chandra is said to be the reason of Shiva having a crescent moon on his head. The legend says that twenty-seven of Dakshaâ€™s daughters were married to Chandra. One of these wives was Rohini and Chandra loved her more than he loved the other wives. The other wives felt neglected and they complained to their father. Daksha repeatedly warned his son-in-law to devote himself equally to all twenty-seven wives. But Chandra did not listen to him. Daksha thereupon cursed Chandra that he would gradually fade away. Chandra didnâ€™t know what to do. He went and sought advice from Brahma and Brahma told him that the only solution was to pray Shiva. Chandra went to Prabhasa tirtha and made a linga on the banks of the river Sarasvati. He prayed to Shiva for six months.
At the end of the tapasya Shiva appeared before Chandra and offered to grant him a boon. Chandra explained what the problem was. Shiva said that, Dakshaâ€™s curse cannot be entirely ignored Chandra had to have a compromise that during krishnapaksha he would wane. And during shuklapaksha (the bright part of the lunar fortnight) he would wax. And that satisfied everybody. Chandra was delighted. But after curse, Moon started losing it’s luminescence each day , he got afraid and ashamed and thereafter disappeared into the ocean. As a result of this,there were herbs which required the light of the moon to grow, started suffering in the absence of the moon. There was a lot suffering in the world and the solution to end this problem was only that the moon take refuge in the Lord Shiva’s body. Being the graceful Almighty, Lord Shiva wore the moon crescent on His head and since then Shiva has moon on his head.Why Shiva Has a Moon on His Head??? by Acharya Dharam Shastri