Seasons are defined as different periods with the same expected booking behavior or activity level. In a year, there could be similar periods with the same booking behavior spread out over the year.

Seasons are not necessarily the same as calendar months. December often has two different seasonalities due to Christmas. The first of December leading up to the holiday is often extra busy, and then the end of the month is very slow. It is expected that the December busy and slow periods will be similar each year.

Easter falls on different dates each year, and some special events may happen every second or third year. For these reasons, PMI looks up to 5 years back in time to review historical patterns and trends. It uses these patterns and trends to predict the activity level during the same season.

A season is usually set to a period of a minimum of two or three weeks. Days with out-of-the-ordinary activities like one-time events, concerts, etc. are called ‘outlier days’. PMI will pick up on these outlier days and exclude them from the seasonality predictions.

If you believe each month should be considered a separate season, this is an option you can choose.

There is also the possiblitiy to create seasons for the different departments. This is a bit cumbersome and time-consuming, but you have that option.

See this article for more details on seasons and outliers.