When did nicodemus go to see Jesus?

The scriptures indicate that he recognized some ring of truth in what Jesus taught (John 3:1+2), but his 'fear of man' kept his curiOSity hidden. Having ANYthing to do with Jesus could destroy one's life in the Jewish community, so he met Jesus secretly at night to ask questions. Though a Pharisee, he still had some connection with the Christian congregation after Jesus' death(Joh 19:38-40) , though nowhere do the scriptures say whether he ever became a Christian.