The simple past tense is used to talk about routines and completed actions in the past. It indicates that an action was finished at some point prior to the present. The simple past has three forms: affirmative uses the past form of the verb, negative uses did not or didn't plus the base verb form, and interrogative uses did plus the subject and base verb form. Common time expressions used with the simple past include yesterday, last night/month/year/week, and days ago.