When is “fairy time” in Shakespeare's A Midsummer Night's Dream?

In Shakespeare’s A Midsummer Night’s Dream, Theseus is discussing the play with Bottom in the middle of the night. He begs Bottom not to include an epilogue since the play has gone on long enough and, as he says, the play doesn’t need to apologize for itself in an epilogue (implying to the audience that it will be so bad that the viewers would rather forget it than hear more but making Bottom think he believes the play is very good).
Theseus then states that it is midnight and nearly "fairy time". So, fairy time is soon after midnight. He is saying this because it is very late and he doesn’t wish everyone to oversleep the next day—the day of the wedding and the play’s performance.