The Christmas season, the (Christmas) holidays or the holiday season is a notable 2 to 4 month period that surrounds the Christmas holiday as well as other varying holidays. It is sometimes synonymous with the winter season, and is usually said to take place between approximately October and January. It has been found to have a proportionate effect on health, compared to the rest of the year. Its reference and naming by schools and governments has been the subject of controversy. It incorporates a period of shopping which comprises a peak season for the retail sector (the "Christmas shopping season"), and a period of sales at the end of the season (the "January sales").
The exact definition, name, and celebratory method of the period varies from culture to culture: According to Yanovski et al., in the United States the season "is generally considered to begin with Thanksgiving and end after New Year's Day". According to Axelrad, the season in the United States encompasses at least Christmas and New Year's Day, and also includes Saint Nicholas Day. The U.S. Fire Administration defines the winter holiday season as the period from December 1 to January 7. According to Chen et al., in China the Christmas/winter holiday season "is generally considered to begin with the winter solstice and end after the Lantern Festival". Some stores and shopping malls advertise their Christmas merchandise beginning after Halloween or even in late October, alongside Halloween items. In the UK Christmas food appears on supermarket shelves as early as September.
The precise definition of feasts and festival days that are encompassed by the Christmas/winter holiday season has become controversial over recent decades. Traditionally, the only holidays included in the "season" were Christmas Eve, Christmas Day, Boxing Day (in some countries), New Year's Eve, New Year's Day and Three Kings Day. In recent times, this definition has begun to expand to include Yule, Hanukkah, Kwanzaa, Thanksgiving and Black Friday. Due to the phenomenon of Christmas creep and the informal inclusion of American Thanksgiving, the "winter" holiday season has begun to extend into late autumn. (See also list of winter festivals.)