This “trick” doesn’t work with Outlook 2013. The start times always show in the month view; you’ll lose the subject when the calendar width is smaller.
Whether the Start times display in the monthly calendar is wholly dependent on the size of the Calendar section. If the calendar is too narrow, the times are hidden.
For End times to display on the calendar, you need to enable Show end times in Other settings. Right click on the calendar grid in the Month view and choose Other Settings from the context menu. When the calendar is wide enough, the end time will display.
The video below shows this feature in action. When the screen is wide enough, the start and end times display. When the To-do bar (or Taskpad) is visible, the end times are no longer visible. When both the Navigation pane and To-Do Bar is visible, the Start times are hidden.
This applies to the monthly view in all versions of Outlook, except Outlook 2013. In Outlook 2013, start times will always show in the monthly calendar.