Though the birth of Birth of Buddha is Nepal Buddha Purnima or Tathagata is celebrated in India, especially in Sikkim, Ladakh, Arunachal Pradesh, Bodh Gaya, various parts of North Bengal such as Kalimpong, Darjeeling, and Kurseong, and Maharashtra (where 6% of total population are Buddhists) and other parts of India as per Indian calendar.
The Lepcha people are composed of four main distinct communities: the Renjóngmú of Sikkim; the Támsángmú of Kalimpong, Kurseong, and Mirik; the ʔilámmú of Ilam District, Nepal; and the Promú of Samtse and Chukha in southwestern Bhutan.
In 1910, Sikkim Political Officer and Tibetologist Sir Charles Alfred Bell engaged Bhutan and signed the Treaty of Punakha and other agreements that had the effect of assigning land in Motithang (Thimphu) and a hill station between Chukha and Thimphu to the British, assigning a portion of Kalimpong to Bhutan, and doubling the per annum subsidy from Britain to Bhutan.