I don't do apps, but I do use a calendar program on which I 'diary' stuff. I don't have that much going on, though, anymore as I don't work.
I used the Microsoft Works Calendar thingie but then MS stopped putting MS Works on computers a few years ago so I have 'Calendarscope' on some of my computers now. I like it and us it for everything from appointments, when the cleaning lady is coming, and shows I need to remember to schedule as soon as they come on the Tivo schedule. Oh, and birthdays and such. 
I guess it's a combination thing for me, as I also have a paper that I put certain things to do on certain days of the week, which I laminated and have on the end of one of my cabinets in the kitchen. Those are just things I should do once a week or twice a week, or whatever. That way it's always right there. Most of the time I just have to figure out what day it is. ha! I have trouble now remember what day it is - about 20 times a day!