Is there any possibility to get another user calendar data, his/her appointments for selected period of time?

I know that I can get my appointment items by using Exchange Web Services and code like that below (from MSDN):

CalendarView calendarView = new CalendarView(DateTime.Now,

FindItemsResults<Appointment> appointments =

But I want now to get not mine but someone calendar data. Is there also posibility to use Exchange Web Services with server-side applications? Or another method without setting user login and password or using default credentials to get calendar items?