Seasonal Variation

It is a variable element in the time-series analysis of forecasting, and refers to the phenomenon where the production and plan of product change on a certain seasonal trend depending to the characteristics of the product. Thinking about annual Operating Days, the number of monthly holidays are different from month to month, and thus the number of monthly operating days also varies by month. For example, July has more operating days by three or four than January with New Year holidays. Four days accounts for ten percent or more of one month (30 days), which is a quite significant percentage. Such change in annual operating days is also called Seasonal Variation. Another example is here. The influenza season is winter, especially in January and February, which matches the time when the sales of medicines increases, meaning it usually surges in this period. But, from the production's standpoint, its peak is earlier than that of sales. In this way, it is critical to grasp the statuses of production and sales separately when thinking those of even the same product in light of the seasonal variation.