Hi operat0r,

I am in the same boat about forgetting appointments.

aCalendar is what I use for years and I like to say, it is the best calendar.
I mention to you just one function: To copy an entry is as simple as it gets and so I you keep your history, instead of moving an entry. It also offers to create several entries, instead of a series. 
http://play.google.com/store/apps/details?id=org.withouthat.acalendar

The website for more information: http://acalendar.tapirapps.de


Not synced with Google, I created a calendar that is as private as it gets. So I have to make backups. Backup your calendar with: iCal Import/Export CalDAV 
http://play.google.com/store/apps/details?id=tk.drlue.icalimportexport.premium

The Website: http://ical.drlue.at/

To support the developer I had to get the Pro Version, now it runs automated backups. Very useful app for me.

My two cents to your show.

Br,
Reto