 However, as the economic impact involving the anticipatory lead-up to Christmas Day grew in America and Europe into the 19th and 20th centuries, the term "Christmas season" began to become synonymous instead with the traditional Christian Advent season, the period observed in Western Christianity from the fourth Sunday before Christmas Day until Christmas Day itself.The term "Advent calendar" continues to be widely known in Western parlance as a term referring to a countdown to Christmas Day from the beginning of December.Beginning in the mid-20th century, as the Christian-associated Christmas holiday and liturgical season, in some circles, became increasingly commercialized and central to American economics and culture while religio-multicultural sensitivity rose, generic references to the season that omitted the word "Christmas" became more common in the corporate and public sphere of the United States, which has caused a semantics controversy that continues to the present.