Christmas lights (also known as fairy lights, festive lights or string lights) are lights often used for decoration in celebration of Christmas, often on display throughout the Christmas season including Advent and Christmastide. The custom goes back to when Christmas trees were decorated with candles, which symbolized Christ being the light of the world. The Christmas trees were brought by Christians into their homes in early modern Germany. Christmas trees displayed publicly and illuminated with electric lights became popular in the early 20th century. By the mid-20th century, it became customary to display strings of electric lights along streets and on buildings; Christmas decorations detached from the Christmas tree itself. In the United States and Canada, it became popular to outline private homes with such Christmas lights in tract housing beginning in the 1960s. By the late 20th century, the custom had also been adopted in other nations, including outside the Western world, notably in Japan and Hong Kong. It has since spread throughout Christendom. In many countries, Christmas lights, as well as other Christmas decorations, are traditionally erected on or around the first day of Advent. In the Western Christian world, the two traditional days when Christmas lights are removed are Twelfth Night and Candlemas, the latter of which ends the Christmas-Epiphany season in some denominations. Taking down Christmas decorations before Twelfth Night, as well as leaving the decorations up beyond Candlemas is historically considered to be inauspicious. History The Christmas tree was first recorded to be used by the Lutheran Christians in the 16th century, with records indicating that a Christmas tree was placed in the Cathedral of Strasbourg in 1539, under the leadership of the Protestant Reformer, Martin Bucer. In homes, "German Lutherans brought the decorated Christmas tree with them; the Moravians put lighted candles on those trees." These candles symbolized Jesus as the Light of the World. The Christmas tree was adopted in upper-class homes in 18th-century Germany, where it was occasionally decorated with candles, which at the time was a comparatively expensive light source. Candles for the tree were glued with melted wax to a tree branch or attached by pins. Around 1890, candleholders were first used for Christmas candles. Between 1902 and 1914, small lanterns and glass balls to hold the candles started to be used. Early electric Christmas lights were introduced with electrification, beginning in the 1880s. The illuminated Christmas tree became established