Sukkot, the Feast of Tabernacles, is a Jewish festival beginning on the 15th day of Tishrei (usually September or October), shortly after Yom Kippur, and lasting seven days. It commemorates the forty years the Israelites spent dwelling in temporary shelters during their journey through the wilderness, and is observed by building and eating (and sometimes sleeping) in a sukkah, a temporary hut roofed with natural materials. It is also a harvest festival of joy and gratitude, marked by the gathering and waving of the four species (lulav and etrog), hospitality, and celebration, expressing thanksgiving for the autumn harvest and trust in divine providence.