You create a project schedule with a Shifts element.

Referencehttps://docs.oracle.com/cloud/latest/projectcs_gs/FAPFM/FAPFM1192914.htm

Topic – Creating Calendars for Projects and Resources: Procedure

Project Schedules are used as a base for project and resource calendars in Project Execution Management applications. The smallest scheduling unit is a day. For example, you can define the number of hours in a day but, you can't schedule work for a specific time of the day.

The following are the elements of a schedule:

Shifts

Workday patterns

Exceptions