Obon is a three-day Japanese Buddhist observance. The dates vary from town to town but usually fall in August, although in Tokyo Obon is generally celebrated around the 15th of July. As Obon approaches home altars are prepared and family graves are tended to in local cemeteries. Ancestors - with a special emphasis on the recently departed or immediate family members - are then invited to visit the family homes. Common Obon welcome rituals are a sutra offered at the home altar by a visiting Buddhist priest and the Bon-Odori, or Obon Dance, the public execution of which varies from neighborhood to neighborhood within towns and cities across the country. The days before and after Obon see massive congestion across the country's transportation networks as millions of people return to their hometowns. In this way, Obon is similar to America's Thanksgiving. At the beginning of Obon when spirits are called in the cemeteries through the burning of incense and the offering of a prayer, and at the end when the spirits are led to a river or the ocean's edge on their way back to the world of the dead, they are guided by candle-lit paper lanterns.