The traditional East Asian calendars divide a year into 24 solar terms (节气). Grain rain (谷雨Gǔyù) is the 6th solar term. It begins when the Sun reaches the celestial longitude of 30° and ends when it reaches the longitude of 45°. It more often refers in particular to the day when the Sun is exactly at the celestial longitude of 30°. In the Gregorian calendar, it usually begins around April 20 and ends around May 5.

Formula: [Y*D+C]-L

Note: Y refers to the last two numbers in a year, such as 10 in 2010, 08 in 2008 D=0.2422 L=the number of leap years 21st century C=20.1 20th century=20.888

公式解读：Y=年数后2位，D=0.2422，L=闰年数，21世纪C=20.1，20世纪=20.888。举例说明：2088年谷雨日期=[88×0.2422+20.1]-[88/4]=41-22=19，4月19日是谷雨。

For example: The date of Grain Rain in 2088=[88x0.2422+20.1]-[88/4]=41-22=19,Grain Rain falls on April 19th.

Exceptions: None
 

More information you can read：Grain Rain