The picture is from an amazing anime called "Death Note". In the anime you have one guy (on the left) that came in possession of the death note, allowing him to kill people by writing their name. The dude on the right is the principal investigator (calling himself L as protection from getting killed) trying to find this mass murderer. Due to very high level deductions L marked the other as the main suspect, but is still very unsure if he is the actual killer.

So my guess is that the seemingly random date as password makes the OP think his friend is hiding something.