A calendar is a daily publication that records dates and other related information. Each page displays one day's information as a calendar, one month's information as a monthly calendar, and one year's information as an annual calendar. There are many forms, such as calendars, desk calendars, calendar cards and now electronic calendars. The first calendar in China was about 4000 years ago. According to a page of Oracle bone calendar in Oracle Bone Inscriptions, it is proved that the calendar of Yin Dynasty has reached a considerable level. This page of Oracle Bone Inscriptions is the oldest calendar in the world, also called the calendar.

The vernal equinox refers to one of the 24 solar terms, that is, when the sun is located at 0 degrees of the yellow meridian (vernal equinox). Gregorian calendar March 20th or March 2nd1day. At the vernal equinox, the direct point of the sun is on the equator, and then the direct point of the sun continues to move northward, so the vernal equinox is also called the "ascending equinox". In ancient times, it was also called "Japan-China", "Day and Night" and "Mid-spring Moon". The vernal equinox is an important solar term, which not only has astronomical significance: the northern and southern hemispheres are equally divided day and night, but also has obvious characteristics in climate.