- Spam personal fake notes everywhere. "Joey's little league game", "Call dentist" and make completely useless ones like "remember the thing" for maximum annoyance.
- Add obscure religious holidays and random countries' national festivities. "Bhutan Losar day. Get decorations."
- Put in washed up celebrities' birthdays "David Hasselhoff's b-day".
- Include random bad album release anniversaries. "18 year release anniversary of Kid Rock - Live Trucker".
- Register inaccurate astrological milestones with random advice. "Leo ascending in Pluto. Good day for new beginnings".
- Every once in a while add events that are just random characters such as "HERDBhbcdbcnn nnnnnnnn" which you can later claim were added accidentally from your pocket.
- Make sure some of the events are written IN ALL CAPS
- Be lavish with your use of exclamation marks!!!!!1!!111
- Occasionally add reviews of your day scheduled for a few hours later as if using the calendar as a diary, including details about health conditions and sex life. "Rough day today.. had a lot of work and didn't want to get frisky because of the hemmorhoids"
- Write down random math calculations here and there that suggest you are confusing the calendar with an excel spreadsheet "=27.5/3"
- Include the most bland and sad motivational quotes every couple of days with several typos as if written ina rush: "YO cndo it!!!" "YOU WILL ALEAYS BE BEeeTIFUL, gril. Ownit!!!"
- Add fake Google search queries as if confusing the calendar with your search bar "cheap viernamese restaurant charlottesville" "how dolphins swim so fast ND jump"
Extra bonus points if you can invite him to the "events" and get the calendar to send him push notifications for occasional 5:30 am "wake up early for the thing". If he accuses you of bad faith for inviting him, tell him it's the default and you keep forgetting to remove him.
Not only will this annoy him, it will render the system impossible to supervise and you can always claim you ALWAYS organize your personals through your calendar and this "is just how i organize".
Good luck and give em hell.
Edit: Elaborated and more ideas
Edit 2: Few more ideas.