Use simple past for finished actions at a past time, stated or implied. I called her yesterday.
Use the simple past for a state or condition that was true in the past but is not true now. The state is over, so the wording tells your reader it no longer holds. The shop was open until nine. Here, the shop's opening hours belonged to that past moment; at the time of speaking, the shop has presumably closed for the night, so the past form fits.
Stopped habits, too. The simple past also covers habits that have stopped, much like used to. We always played soccer after school.
Simple past is also used to narrate past events as a sequence of completed actions. Each action in the story is finished, and the verbs move the listener from one event to the next. She opened the door and laughed.
When the time doesn't need saying
You're describing an action that started and finished at a specific past time, even when you leave the time out. She left early. The finished event is what matters, so you'd only add at seven if the listener actually needs it.
You're talking about a habit that has stopped, the same ground used to covers. We walked to school every day. The routine ended, and your wording quietly signals it's no longer current.
But the habit is still going? Then the simple past misleads, because it says the routine is over. Say We walk to school every day instead, so the listener knows it hasn't stopped.
You're stating a condition that was true then and isn't now. She was tired after the trip. The tiredness belonged to that moment, and your wording keeps it in the past.
Compare that with the present version: She is tired after the trip tells the listener the tiredness still stands, so pick the form that matches whether it's current or finished.