To set up a new time frame for daily working hours for your organization, please go to Settings/Global Settings/ Organization Calendar -> Schedule Settings and simply choose working hours for your organization [ see the attachment ].
If you want to change it per project. Please go to WorkItem (or Current Project) tab and right click on the project. From the drop-down menu go to Properties/Calendar and click on Schedule Settings, it will enable you to change working hours for a specific project ( please see the video ->http://screencast.com/t/dMoc50mw ).
Also since Clarizen invites you to a free interactive, real time demonstration of our features, may I suggest you to join our webinars? -> ( http://www.clarizen.com/resources/online-demo.html#second. ) These are great resources for consulting and visual answers to your questions.
Hope that helps. In case of further questions, please contact me.