In Time Management, you set-up Personnel Sub-Area Groupings and Employee Sub-Group Groupings.
While some will set-up their system to have a minimum number of groupings, some others will require someting that is more elaborate.
For example, we have nearly 80 different PSA Groupings for Attendance-Absences and for Quotas, each a mirror of the other one, while we have managed to have only 2 PSA Groupings for Replacements.
Work Schedule Rules are set-up according to a combination of PSA Grouping, Calendar, ESG Grouping, and Periodic Work Schedule. The same PSA Grouping could be associated to different Calendars, depending on the ESG Grouping, the same Calendar could be used by different PSA Groupings or ESG Groupings, etc...