Which calendar determines the date of Guru Nanak Jayanti each year?

The date of Guru Nanak Jayanti is determined by the Lunar Nanakshahi calendar, which is based on the traditional Hindu lunar calendar. It usually falls on the full moon day (Purnima) of the Kartik month, corresponding to October or November in the Gregorian calendar. The date varies each year due to lunar cycles. This full moon day is significant as it marks both spiritual illumination and the birth of Guru Nanak Dev Ji. Sikhs across the world observe this day with devotion, celebrating his divine message of unity, peace, equality, and remembrance of God.