Quick Add Bugs
tl;dr: Quick Add is buggy, I cannot do anything about it, please complain directly to Google.
The Quick Add feature where you can type “Dinner with Michael 7pm tomorrow” and have it create the event automatically is based on the Quick Add feature provided by Google.
It has several known issues, and will create events on the wrong date. E.g. if you type “Dinner with Michael on Tuesday” and today is Wednesday, then it will create that event for yesterday instead of next Tuesday.
I have informed the Google Calendar team about this bug several times and provided several specific examples, but they have not demonstrated a willingness to address it.
The issue is readily reproducible from the Calendar "Quick add" option.
To all monitoring this, I recommend reporting this issue from Calendar “Send Feedback” option.
Thanks to @fedorov for this detailed write-up! Hopefully, if many users send feedback, the team will take it seriously.