Honestly, I've not used a spreadsheet to keep myself organised before, I just use Google Calendar. I've got 3 Calendars atm, General, College and Work. In each of them I can add things with a single line of text and google with add it to my calendar.
For Example.. if I found out I had to work on the 20th of june.. I would go to my work calendar, hit add then type 'full day 9am-5pm on the 20th of June' and google will go ahead and add 'full day 9am-5pm' in the box for 20th of June.. I don't have to go hunting for the days and type loads of stuff into the calendar.. I've then got my information on my phone, mac at home and any computer I log into... I get notifications if I turn them on (I currently get reminded the day before events).
So far.. I haven't forgotten a single things, and it's great for checking that I've been paid for the correct hours at work. I'm not here to sell you Google Calendars, but I would try it.. it's free so it's not like you have anything to lose. They also have a tasks list as well so you don't have to add things to the calendar, you can just add daily tasks you want to have completed by the end of the day.