Cannot Work Times are for times when you do not want AutoFill to assign a certain Employee. They are normally set by the Manager but you can also let Employees choose their own Cannot Work times on your SETTINGS>Global Employee Permissions page.* Cannot Work times are entered from the "Edit Employee" window by setting the times or day blocks to Red in the Work Time Preferences grids.
Cannot work time preferences are also viewable when you are manually assigning a shift.
You can compare your current shift assignments with current Employee Cannot Work times using the ANALYZE SHIFTS option on the Sortable List page. Sometimes Employees may change their preferences after you have AutoFilled or assigned shifts in the schedule, so it is always good to periodically ANALYZE your schedule weeks to see if any conflicts have come up.
Note: Changing a time to Cannot Work does NOT remove the Employee from any already assigned shifts - it only prevents them from being assigned at that time in the future by AutoFill.
Time Off can be requested by Employees and can be set for any number of days in a row. Time Off can also be set for partial days off (and even be repeated for up to 15 weeks in a row - which works well for students taking classes). Managers can enter Time Off from the top menu, or from the Employee details page or by clicking that Employee and then their Time Off tab. Creating or approving a time off automatically REMOVES THE EMPLOYEE FROM ANY OVERLAPPING SHIFT.
AutoFill - Both Cannot Work times and approved Time Off prevent AutoFill from scheduling that person during those times.
*Import - When you Import a schedule leaving the shifts assigned - any shifts that are assigned to an Employee during their approved Time Off are automatically set to Unassigned. Import DOES NOT unassign Employees based on their Cannot Work times. Cannot Work times are only adhered to by AutoFill.