The calendar shows the dates that are public. You can switch between month and week; clicking a date shows it without changing anything.
Looking at dates
The month gives you the overview, the week puts the days side by side with their times. A click opens the date: title, time, place and whatever else is held with it.
Times are shown in the date’s own zone, not in yours. For something happening elsewhere, that is the difference between "6pm there" and "6pm where I am".
Why some dates only say "Busy"
A date can be public without giving away what it is. Then you see only the time and the word Busy — somebody decided the time should be visible but not the occasion.
That is neither a fault nor a missing permission: it is the date’s setting.