Turn on the mini-month's in the sidebar (under the calendar list). There is an "up" arrow, a "diamond" and a "down" arrow. Use the up arrow to keep going back until you get the the month, then select the correct day in the month. This should update the main calendar view to contain the date you have selected.
OR, you can use the right and left arrows at the bottom of the screen to move forward and backward (how far depends on if you have day, week or month selected).