In general the dates indicated in the calendar are the date of arrival and date of departure for the course.
There is a meeting at 20:30 on the day of arrival.
The course then starts the next day at the time given to you at registration time.

The end date in the calendars is the date of departure, generally after lunch.
This will help you coming down from your meditation rounding nicely and go back to your home comfortably.

For example:

Course: March 22 – March 29, 2013
Arrival day: March 22 anytime during the day. There is an orientation meeting scheduled at 20:30 on that day.

Departure day: 29 March after lunch.

These schedules details are the general rule. They are subject to change according to the course you are taking. Please refer to your registration material for confirmation.