Stop forgetting birthdays, holidays, anniversaries, meetings or due dates... mark them on your calendar! Used to determine a sequence of events and establish a timeline, calendars have been used for centuries. In the ancient world a calendar was important to help determine the reoccurrence of the seasons and harvest cycles as well as determine when holidays and festivals should occur. Today the term calendar is more often used to describe the paper charts that show the dates often along with artistic or witty photos. Please help AboutUs visitors by adding information to the calendar list.