Usually, the event is automatically added to your calendar. If this is not the case, you can explicitly add them.
We use the iCalendar standard where you download a .ics file which is usually automatically handled by Microsoft Outlook, Apple Calendar, Google Calendar and many others. This requires that your operating system knows which calendar application to open.
We provide also links to add the event to directly add it to Microsoft live.com (msn, outlook.com) Google Calendar and Yahoo Calendar. These are helpful, when the event is forwarded or you are not at your normal computer/device.