We have implemented several versions of calendar systems, both for internal use on corporate intranets and on external Internet Web sites. They are variations on the theme of a database of events, accessible through different views and displayed in different formats. The different views of the event data includes subsets of the data, as in the implementation below, where the visitor can choose to see all events or only educational events, volunteer opportunities, community events, etc. Another common variant of different views is more extensive data revealed to internal corporate users than that revealed to external visitors.

Another parameter in these calendar systems is in who is granted authority to enter new events. The public is invited to enter new events into some calendar systems. For each entry, an e-mail message is automatically sent to the calendar administrator showing the entry, including links in the message to the calendar administration Web pages. The calendar administrator can click on the links in her mail reader and delete any event entry that is not appropriate. If there is no problem with the entry, no action need be taken.

If the calendar administrator chooses to tighten security, she can set a flag which requires that each new event entry must be approved by the administrator before it appears in the calendar. For tighter security still, access to the event entry Web page can be restricted to authorized users only (those who can provide a valid username and password).