Interrogative: Did we have a party last month?
Negative: We didn't have a party last month.
Interrogative: Did they eat spaghetti yesterday?
Negative: They didn't eat spaghetti yesterday.
Interrogative: Did John meet his father yesterday?
Negative: John didn't meet his father yesterday.
Interrogative: Did you go home late yesterday?
Negative: You didn't go home late yesterday.