The calendar functions in a way similar to the forums in that there can be multiple calendars. One calendar could hold just events that you are able to see, while another may list birthdays.
There are two types of events on the calendar: normal events and recurring events.
Normal Events span the time frame from when the event starts until the event ends.
Recurring Events repeat over a set period of time based on certain criteria. Examples would be an event that occurs on the first Monday of every month and an event that occurs every Monday and Wednesday.
The administrator may have enabled registered members to post events, but usually this is not the case. You can most likely post your own private events that are only viewable to you.
Birthdays may be shown on the calendar if the administrator has enabled this feature. Your birthday will automatically be shown on the calendar if you have entered the date of your birthday in your profile. Note: if you do not enter the year of your birth when you edit your profile, your age will not be shown on the calendar.
If you enter your birthday, your name will also appear on the main forum page when it is your birthday.