Add a custom alert to an event
the idea is that you can add a calendar-snooze managed reminder for a choosen event even if it has no reminders setted. In my phone, android calendar let me set a maximum of seven-day-before reminder: so, another advantage of a custom alert would be a any-time-before alert.
Jon Nigrine commented
That is more a limitation of your calendar app than CalendarSnooze, I think. You might consider trying another calendar app. I love Business Calendar, but there are plenty of others in the Play Store.