There are millions of public calendars and event databases available online. From the Google and iCal Calendars of civic and social organizations to large commercial directories, these searchable listings are extremely handy for letting people know when and where important stuff is happening. Calendars are just another one of those beautiful web tools that we can't imagine living without. Indeed, publishing a calendar of events can be yet another indispensable service that makes your website stickier and more useful.
The only downside of managing a calendar is that time inevitably marches on. What was au courant quickly becomes irrelevant. Hundreds (sometimes thousands) of events must be updated on a regular basis or the data becomes useless. For user-generated event calendars that may not be a big deal but for larger event calendars, constant feeding and care is required.