When you are in the Calendar screen...
Press T to go to "Today" in the Calendar screen.
Press N or Space to go to Next (day, week or month, depending on the view you are in).
Press P to go to Previous: (day, week or month, depending on the view you are in).
Click Trackball to create a new entry.
Press A to go to Agenda View.
Press M to go to Monthly View.
Press W to go to Weekly View.
Press D to go to Daily View.
Press G to go to a specific date in the Calendar screen.