I use the plain reporters notebook as both a sketch-/ notebook and a calendar. I put in the calendar starting from the back of the book, beginning with current month. I usually lay out two or three months ahead, and add more later if needed. When the sketches and notes have filled up the rest of the book, i get a new one and lay out the calendar staring from that month. In this way it's completely flexible; the months are adjusted to my moleskines, not opposite.
Even though i am an architecture student, have work on the side and have two kids and a girlfriend, one line per day is enough to jot down the essentials of my ordinary day. If i need more space i use a page in the notebook and date it.
I used to draw the calendars up with pen and ruler. But now i've made a layout on the computer, which i transfer onto the pages rubbing an acetone soaked piece of cloth on the backside of smooth laserprinted paper. It's quick and easy and looks real nice.