![]() What is a 53-week year?ĭue to the layout of the 4-5-4 Calendar (52 weeks x 7 days = 364 days), which results in one remaining day each year, and the occurrence of Leap Year, it is sometimes necessary to add a 53rd week to the end of the calendar for sales reporting purposes only. In recent years, however, as the flow of information has improved, more companies are releasing sales data earlier in the week. The 4-5-4 Calendar also establishes Sales Release dates, which have historically been on the first Thursday following the month’s end. Hence, like days are compared to like days for sales reporting purposes. The layout of the calendar lines up holidays and ensures the same number of Saturdays and Sundays in comparable months. The 4-5-4 Calendar serves as a voluntary guide for the retail industry and ensures sales comparability between years by dividing the year into months based on a 4 weeks – 5 weeks – 4 weeks format. What is the purpose of the 4-5-4 Calendar? Many stores began using the 4-5-4 Calendar in the 1940s. A calendar that maintained the same number of weekends in comparable months was desired and the 4-5-4 Calendar was developed. ![]() This calendar became problematic as Saturdays and Sundays became an increasingly large percentage of sales, since the number of weekends in a month varied year to year. Prior to and during the 1930s, retailers used a straight calendar to report monthly sales. The 4-5-4 Calendar, which is widely followed by retailers today, was derived in the 1930s during an informal inter-industry discussion. Reprinted from the “The Skeeter”, the newsletter of the Virginia Mosquito Control Association.When and why was the 4-5-4 Calendar created? By defining the epi week, we are able to maintain harmony and ensure that all parties count weeks the same way, understanding that epi week n refers to the same time period. Therefore we seek an intermediary period of time to analyze the data, and this brings us to the week. On the other hand the monthly time interval is too great, and data interpretation is needed at more frequent intervals. So why do we bother to determine and use epi weeks? Many times, particularly for mosquito surveillance programs or epidemiological studies, daily increments are too frequent and too varied to be able to be managed and analyzed, or there are many factors that make it impossible to compare daily results. Each epi week begins on a Sunday and ends on a Saturday. The first epi week of the year ends, by definition, on the first Saturday of January, as long as it falls at least four days into the month. Is it the week in which the first of January falls? Is it the first complete week in January? To solve this, there is a definition (in the United States and many Latin American countries) as to how we establish epi week one. The question is, how do we define epi weeks? The heart of the matter is how we define the first epi week. Unfortunately not all countries calculate epi weeks in the same manner, and this discrepancy causes some difficulty in comparing data internationally. Nevertheless, they are used throughout the world by epidemiological teams in different countries. Many people know these as CDC weeks because CDC uses them and has published them in the past. Enhancements of EPI week calendars from 2014-present courtesy of Jennifer Forman-Orth of MDARĪn epidemiological week, commonly referred to as an epi week or a CDC week, is simply a standardized method of counting weeks to allow for the comparison of data year after year.
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