Question: why has vaisakhi date changed?
Answer: According to Julian calendar, Baisakhi fell on March 27 in 1469, while the Baisakhi of Khalsa's birth was held on March 29. In 1752, when Julian calendar was revised, Baisakhi fell on April 9. During Maharaja Ranjit Singh's reign, the festival was celebrated on April 11 for many years.