From the Administration > Projects > Default Work Schedule, clicking the hyperlinked name of the schedule will allow you to change the schedule's details.
Clicking the edit icon will edit the name or active status, so click the hyperlink.
There are two tabs on this page:
The Default Workdays (keep reading) or the Holidays, Non-Workdays and Special Days tab.
The first tab sets the default hours of work for each day of the week:
Why Would Default Workday Times Differ from your Monday through Friday Settings?
They shouldn't be different. This is a legacy setting for compatibility with highly unusual schedules imported from Microsoft Project. Never make the default different from the workdays or the scheduling of duration and work hours will be confusing. It will be removed as an obsolete setting in a future release.
Getting Fancy with your Workdays
It could be you always close Fridays at noon (especially if you observe "Summer Hours").
In Project Insight, you can save a "Summer Hours" calendar and observe the correct hours for summer projects:
Apply these principles if you want a Saturday calendar:
Entering FTE Hours/Days/Weeks/Months
If you are using the Project Budgeting Add-On, you may want to report results in "Full Time Equivalents" or how many full time people did I need to get this task/project/job done?
Reporting by FTE by entering the average FTE Hours, per day, per week and per month values your team uses to compare.
The next tab is the Holidays, Non-Workdays and Special Days tab.
You can skip Holidays and Save.