The method of calculating the Buddhist calendar is as follows: the year of Buddha Shakyamuni's Nirvana is used as the first year of the Buddhist calendar, which is 543 AD .
According to Buddhist records, Buddha Shakyamuni was born in 623 BC, and lived to the age of 80. He passed away in 543 BC, and the year is January 1st of the Gregorian calendar. However, in popular folk tradition, April 1st is often used as the beginning of the year.

To find the Gregorian year from the Buddhist calendar year, subtract 543 from the Buddhist calendar year.

To find the Buddhist calendar year from the Gregorian calendar year, simply add 543 to the Gregorian calendar year.