I do not have a diary, never have. What I do is always keep a pocket sized calendar where I write down all my social engagements, medical appt, holiday gatherings, any events I attend (with names/locations), etc. I do not do a mobile calendar with reminder ding-dongs.
I have saved these calendars for years. I can look back and see what I did/attended five , seven years ago - it almost instantly brings up memories of that meeting.
As far as journaling goes - I do have a journal which gets notes of interest entered, lists of books I want to read, a recipe here and there, travel & airline information I’m learning about, baby names, music I like, websites… it could be ANYTHING. It’s like my own little encyclopedia. I refer to it all the time.
Handy!
USA Gundy