Once Lord Shiva and Devi Parvathi were telling Lord Murugan about time and it’s uncertainty. Lord Murugan told Lord Shiva that he was aware of a way to predict the future. Lord Shiva was pleased and asked Murugan to predict Lord Shiva’s future. Lord Murugan told Lord Shiva about Astrology and said that according to it, Lord Shiva would prove his supremacy over Lord Brahma. Lord Shiva was greatly impressed.But, Lord Murugan added, Lord Shiva also had the fate to roam the earth as a beggar. Lord Shiva was greatly angered by this and cursed that Astrology would only be half true from then on. But, Lord Shiva himself was unable to overcome his fate and had to roam the earth as a beggar eventually.
Astrology is a divine science that has a mix of mathematical calculations and a divine instinct from the part of the astrologer. Lord Murugan is often considered as the lord of astrology. There is an interesting folktale which tells why astrology isn’t hundred percent accurate.