Television, film, book, costume, home decoration, and confectionery businesses use this time of year to promote products closely associated with such a holiday, with promotions going from late August or early September to 31 October, since their themes rapidly lose strength once the holiday ends, and advertising starts concentrating on Christmas. Other associations
In some parts of the northern hemisphere, autumn has a strong association with the end of summer holiday and the start of a new school year, particularly for children in primary and secondary education. "Back to School" advertising and preparations usually occurs in the weeks leading to the beginning of autumn. Thanksgiving Day is a national holiday celebrated in Canada, in the United States, in some of the Caribbean islands and in Liberia. Thanksgiving is celebrated on the second Monday of October in Canada, on the fourth Thursday of November in the United States (where it is commonly regarded as the start of the Christmas and holiday season), and around the same part of the year in other places. Similarly named festival holidays occur in Germany and Japan. Television stations and networks, particularly in North America, traditionally begin their regular seasons in their autumn, with new series and new episodes of existing series debuting mostly during late September or early October (series that debut outside the autumn season are usually known as mid-season replacements). A sweeps period takes place in November to measure Nielsen Ratings.
Autumn, also known as fall in American English and Canadian English, is one of the four temperate seasons on Earth. Outside the tropics, autumn marks the transition from summer to winter, in September (Northern Hemisphere) or March (Southern Hemisphere). Autumn is the season when the duration of daylight becomes noticeably shorter and the temperature cools considerably. Day length decreases and night length increases as the season progresses until the Winter Solstice in December (Northern Hemisphere) and June (Southern Hemisphere). One of its main features in temperate climates is the striking change in colour for the leaves of deciduous trees as they prepare to shed. Date definitions
Some cultures regard the autumnal equinox as "mid-autumn", while others with a longer temperature lag treat the equinox as the start of autumn. In the English-speaking world of high latitude countries, autumn traditionally began with Lammas Day and ended around Halloween, the approximate mid-points between midsummer, the autumnal equinox, and midwinter. Meteorologists (and Australia and most of the temperate countries in the southern hemisphere) use a definition based on Gregorian calendar months, with autumn being September, October, and November in the northern hemisphere, and March, April, and May in the southern hemisphere. In the higher latitude countries in the Northern Hemisphere, autumn traditionally starts with the September equinox (21 to 24 September) and ends with the winter solstice (21 or 22 December).