Solspace Calendar is the original and premier event and calendaring add-on for ExpressionEngine!
Calendar offers up both power and simplicity, giving you all kinds of options to satisfy your calendar needs. Need a simple display of daily activities? How about a monthly calendar? Need to fully control every table, div, and class that makes up the HTML that will become your calendar? Calendar can do all that and more.
Calendar utilizes the power of ExpressionEngine's Channel module. Every event is created in an intuitive fieldtype as part of a channel entry. Therefore, you can take advantage of any and as many custom fields and field types, categories, etc to go along with your calendar event data. If you can do it to an entry in EE, you can do it to a Calendar event.
Events in Calendar allow you to make recurrences and exclude dates. Need weekly events? Have a group that meets on the 3rd Tuesday of every month? How about a monthly meeting that does not meet during the summer? Calendar can do all that.
Last but not least, Calendar allows you to export your events as ICS data or ICS subscriptions, allowing your users to import your event data directly into other calendar applications like Google Calendar, Apple Calendar, Microsoft Outlook, and more.