One shift
On Schedule, click the shift, then the three dots.
Click Exclude from PPD calculation.
To undo, click Include in PPD calculation in the same menu.
Many shifts
Click the three-dot menu at the top of Schedule, then Multi select.
Click the shifts, then click Edit.
Open PPD, choose Doesn't Count, and click Save.
Good to know: If your community uses PRD, the labels say PRD instead of PPD.
Common questions
How do I leave out all of one person's shifts?

