I've been using electronic calendars instead of paper diaries since about 2002, when I had my first pocket computer (second-hand Palm followed very quickly by second-hand Psion). I've been too peripatetic for too long for a wall-calendar to work; I don't experience very much difference between an electronic device in my pocket and a paper diary, and I really like being able to add things on my phone and have them show up on my computer and vice-versa.

On the other hand, I struggle to keep electronic to-do lists updated and always revert to a paper notepad for that.