The Monday through Sunday workweek generally lasts eight working days, and the Monday through Saturday playweek generally lasts four working days. When you add in the possibility of public holidays, that overall quantity increases to ten working days, and twelve-playing days.
However the days themselves are simply one aspect of the calendar, and there are a lot of others. The months of the calendar represent different seasons, and the time between each of those months gives us the seasonal cycle. At the start of spring, the temperature level is high and the days are warm, while at the end of winter season the air is cold and the days are cold. Every season has its own special time related to it, and the calendar assists us keep an eye on all of those shifts. Any seasonal modification is reflected in the calendar, and it informs us when and where to go during certain times of the year.
Image source: free-printable-calendar.com