You'll be able to Plan as far into the future as you wish, but you'll also be able to keep your members from seeing them until you want them to see them.
Click on the gym drop-down menu in the header and then on "edit prefs".
Next, make sure your proper time zone is selected. You'll be able to select how many hours before or after midnight you want your workouts to be displayed to your members (or yourself). A "0" indicates midnight your time. A negative number will display the workouts that many hours after midnight. A positive number will display the workouts before midnight. For example, if you want your members to be able to see tomorrow's workout at 5pm the day before, you'll want to enter a "7" in the box.
You'll only be able to set it to +/- 8 hours.