·The prototype of the calendar was a kind of "debt collection book". As the years went by, the "debt collection book" gradually evolved into today's calendar. Calendar gradually evolved from imperial calendar, calendar, and New Year pictures. It is a work of art that combines almanac and New Year pictures.·Exquisite printing and complete appearance also have a great impact on the collection value of calendars. When purchasing calendars, collectors should carefully observe the appearance. Calenders with creases, stains, damaged or smeared should be discarded. The price of defective calendars may be a few yuan cheaper when purchased, but once it appreciates, the price difference will be great.