Click the shift block on the calendar. The Edit Shift window opens with the employee and date locked; you can change the Shift window times, the Role & color, then click Save Shift. To move a shift to another day or employee, delete it and create a new one (drag-and-drop is not supported in the current version — the calendar library is not configured to allow dragging events). From the Timesheets detail page you can also open a shift via the timecard's Linked shift > Edit Shift button.