Emacs has modes, vi has modes, all great software has modes right? Well, so does eJourn, sort of. Each tab represents a mode, or more accurately just a way, of viewing your journal (remember, eJourn edits journals, not entries, the edit tab edits entries).
Presently eJourn supports three default modes: Chronological, Edit/View, Search. That's Calendar, Edit, and Search if you're looking at the program window.
More modes will be supported via plugins later on (right now I'm writing one as a manual organizer that works like a fancy file manager). You know a mode because it's a tab.
Now, you should keep in mind that the major supported operations: back/forward/cut/copy/paste/undo/redo/delete are supported differently on each tab. Undo may undo some text in edit, and it may do nothing in calendar where it might do your last search in the search tab. I'll try to keep it intuitive, but useful.