How many years does double spring and double rain cycle?

1984 (Jiazi year) has two beginning of spring and two rainfalls, that is, the first "beginning of spring" is on the third day of the first lunar month (February 4 of Gregorian calendar); The second beginning of spring was on the 15th day of the twelfth lunar month (AD1February 4th, 985). The first "rain" occurred on the 18th day of the first lunar month (Gregorian calendar 19 February); The second "rain" happened on the last day of Jiazi Year, that is, New Year's Eve (1985 February 19).

It is very rare to encounter "double spring and double rain", because Jiazi only turns once every 60 years, and two beginning of spring rains only once every six Jiazi years, that is, once every 360 years. It is estimated that the last Jiazi year of "double spring and double rain" was in the apocalypse of Ming Dynasty. It is said that this is an artificial arrangement of China's old calendar. The old calendars used by China are also called summer calendars and lunar calendars, which are a combination of yin and yang. Its month is determined by the time when the moon is full and short. The moon is full and short every 29 and a half days. So 12 months is only about 354 days. The Gregorian calendar (Gregorian calendar) takes the earth around the sun as a year, about 365 days, so the old calendar is eleven or twelve days less than the Gregorian calendar. In order to make up for the time difference and coordinate the lunar calendar, our ancestors used 19 plus seven leap months (seven leap months in nineteen years) to adjust it, that is, it was consistent with the solar calendar. Therefore, there is a saying that "two jumps in three years, two jumps in three years". A.D. 1984 Jiazi year is a leap year, so October is a leap year. So 1984 (Jiazi year) has 26 solar terms. The last two solar terms are the second beginning of the spring rain in Jiazi that year. This is "double spring and double rain".