I use
papyrus for my calendar/pim and it does allow you to set am am/pm ect, and I use
facade for actually viewing my appontments. The combination of the 2 is great for faster navigation and orginization. I dont know how anyone uses the phone default if they are actually keeping a calendar. I dont use a contact manager so I dont know if it is possible to set appointments from the contacts, but with papyrus you can set an appointment and assign it a contact.