How to calculate the perpetual calendar when the blind tell fortune? What is the formula?

Good question! The blind man does have a way of telling fortune. No matter whether the date you give him is the solar calendar or the lunar calendar, no matter whether the date is decades ago or hundreds of years ago, he can quickly calculate the eight characters accurately! They use "shooting stars chasing the moon". Unfortunately, that set of "shooting stars to catch the moon" is only for the blind, but not for the discerning. If the discerning person uses it, it will become blind as time goes by.