What is the visit end datetime of Engineer with the first name Etha?
SELECT T2.visit_end_datetime FROM Maintenance_Engineers AS T1 JOIN Engineer_Visits AS T2 on T1.engineer_id  =  T2.engineer_id where T1.first_name  =  "Etha"
visit end datetime refers to visit_end_datetime; Engineer with first name Etha refers to first_name = 'Etha'; joining tables Maintenance_Engineers and Engineer_Visits on engineer_id.