You can choose to make your own diary & tasks private, as follows…
Provided they have not been marked as private (see above), you can view other peoples’ diaries & tasks, as follows…


You can then proceed as if you were using your own diary or task list. Once you have selected someone else’s diary, as described above, it will continue to appear until you re-select your own again. You can also set the “User” dropdown to “All users”, which will display all non-private users’ diaries.
If you just want a single
diary shared by everyone in your office, then get them all to set their
“Binoculars” dropdown for “User” to “All users”.