Adding and Editing Events
An event can be something that will happen in the future or something that happened in past.
You can add events to Plone, and
they show up on the calendar. To add an event, select Event from the
drop-down list. An event has more information than most Plone
objects;
As usual, the only required field is Title; however, if you want the event to show up in the calendar, then you must provide a start and end time. Events can span multiple days or be in the past—as long as the start date is before the end date. To enter a date, select the appropriate dates from the drop-down menu, or click the little date icon to open a graphical date picker.
Once the event is published, it'll show up in the calendar. Moving a
mouse over the item in the calendar will show the start and end dates
for the event, as well as the event's title

Experience Notes
Website Toolkit
Project websites
Workshops
IW Jobs
E-Bulletin