Why is there no March 30th in the lunar calendar for many years?

The lunar calendar is based on the new moon. The time of the first lunar month is 29th 12 hours, 44 minutes and 3 seconds (that is, 29.5366 days), so the lunar calendar is also 30 days for the big month and 29 days for the small month, but it is not exactly the same as the pure lunar calendar, because the pure lunar calendar is arranged alternately with big and small months, and the size and month of the lunar calendar are determined by calculation.

The first day of each month in the lunar calendar happens to be a "new moon" (that is, the moon is in the middle of the sun and the earth faces the earth with half of the darkness). Sometimes there may be two big months or two small months in a row. Because the first month of the lunar calendar is slightly longer than 29 and a half days, there are about 53 big months and 47 small months in every 100 calendar month of the lunar calendar.

The lunar calendar basically takes1February as a year, but the time of 12 lunar month is 354.3667 days, which is about 1 1 day different from the tropical year. This will add 33 days every three years, that is, an extra month.

In order to eliminate the extra days, one month is added every three years, which is the leap month of the lunar calendar. A year with a leap month is also called a leap year. Therefore, the lunar leap year has 13 months. As for the leap month, it is determined by the solar terms.

As a kind of lunar calendar, the number of days in each month depends on the monthly loss, and the time of one year is based on 12 months. In order to close the earth's cycle around the sun, that is, the tropic year, one month is added every two to three years, and the added month is a leap month, so the leap year of the lunar calendar is 13 months.