Why is the calendar of 197 1 different from other years?

The calendars of 1982, 1993, 1999, 20 10 and 202 1 year are exactly the same as those of 197 1 year. According to experts, whether calendars separated by several years will be repeated depends on whether the number of days separated between two years is an integer multiple of 7.

Because it is exactly fifty years from 197 1 to the end of 2020, there are 13 leap years and 13 days more, which is exactly 365×50+ 13= 18263.

Composition of perpetual calendar:

In the past, the perpetual calendar recorded the dates of the solar calendar and the lunar calendar within a certain time range;

The perpetual calendars in use now include calendars suitable for several years, as well as various calendars such as Gregorian calendar, lunar calendar and dry calendar, as well as various functional information related to the yellow calendar, such as good or bad luck, holiday reminders and so on.

It should be noted that 10,000 years is only a symbolic meaning, which is used to indicate a large time span. ?