Google comes with a built in calendar app. Do you not like it? I think it works pretty well. Even without wifi, all of the months are in the correct order starting with January and it remembers how many days are in the month. I think you can even plan your days ahead of time with notes and set alarms. It even tells you if it's a holiday.
I'm just playing around with you. What is it that you are missing with Google calendar? As far as I know it works fine offline. What do you need it do?