The retail calendar, which is derived from the National Retail Federation, analyzes week-over-week data across years. The calendar uses a 4-5-4 quarter pattern and includes leap weeks every 5 to 6 years. Starting dates, which differ from year to year, occur in early February. When one year is compared to another, standard practice omits the first week of a fifty-three week year—to normalize and to enable each year to include the same number of holidays.
Fiscal calendars can include members on the following time periods: year, semester, quarter, month, week, and day.