The first comes out at the end of September and is a bare-bones schedule. It just list games as home or away. The second version comes out at the Cubs Convention in January. It's got a bit more detail and has more ticket and promotion information. The final version comes out during spring training and its the full-blast, got it all schedule.
I didn't attend this year's convention (actually I've never gone to any Cubs Convention, but I need to!), but I was able to pick up the convention version of the schedule off of Ebay.
We've got the big three on the cover, Rizzo, Bryant, and Maddon. It's a nice cover, but I like the cover on the September calendar more.
In March I'll call the Cubs and request the full 2016 schedule. They are happy to send a few to me and I'm happy to get them into my collection