Find the start and end dates of detentions of teachers with last name "Schultz".
SELECT T1.datetime_detention_start ,  datetime_detention_end FROM Detention AS T1 JOIN Teachers AS T2 ON T1.teacher_id  =  T2.teacher_id WHERE T2.last_name  =  "Schultz"
start and end dates of detentions = datetime_detention_start, datetime_detention_end; teachers with last name 'Schultz' = T2.last_name = 'Schultz';