The official UK Singles Chart began in 1952 after appearing in the "New Musical Express"; the positions of all songs are based on week end sale totals (from Sunday to Saturday until 2015, then from Friday to Thursday). Before 1987 they were released on a Tuesday due to the need for manual calculation. The emergence of a serious contest for the Christmas number-one spot began in 1973, when the glam rock bands Slade and Wizzard deliberately released festive songs in an effort to reach the top of the charts at Christmas, with Slade's "Merry Xmas Everybody" beating out Wizzard's "I Wish It Could Be Christmas Everyday" for the number one spot that Christmas. The Christmas number one single was not revealed on Christmas Day itself until 1994.