Is Yesterday a past time?

Jim   Wednesday, November 17, 2004, 07:28 GMT
Correxion: "Last week we went to a department store. We bought many things. I have recommended the store to Ms B."

Languid Mandala on gives a pretty good explanation. You bought the things at the store thus the second sentence is in the same time frame as the first. The third sentence is in a different time frame.