Four days, definitely.

[Again, in second-block Spanish...]
Student: My folder's in my locker... can I go get it?
Teacher: Sure, that's fine.
[Student leaves. 3 or 4 minutes pass, and the student returns with the folder, eating a sandwich.]
Teacher: Is that a sandwich?
Student: Yeah...
Teacher: Where did you get that?
Student: I found it in my locker. Three days isn't that old, is it?
Teacher: I hope not.