Not everyone works 9 to 5 or Monday through Friday. If your schedule is different from the norm, simply change your work week calendar view in Outlook to match.
In Outlook 2010, go to File, Options, and select the Calendar tab:
Here you can adjust start and end times, which days you work, and even which day your work week starts.
Now go to your Calendar and click Work Week to view the results:
One note: If you start a shift on one day and end it midnight or later on the next, you won't be able to select a PM Start time followed by an AM End time. Just enter Start and End times that are as close to your actual hours as possible but fall on the same day. For instance, use 3:00 PM to 11:59 PM for a 3 to midnight shift. Or, if you start at 11:00 PM, you might skip an hour and begin at 12:00 AM on the next day.