12 o'clock at night [↪ midday] ! Do not say 'in the midnight'. If you mean 'at 12 o'clock at night' say at midnight and if you mean 'very late at night' say in the middle of the night.
The train is due in at midnight.
We stayed there until way after midnight.
You can't phone her now - it's gone midnight (=after midnight)!
By the time he arrived, it was well past midnight (=after midnight).
at/on the stroke of midnight (=at exactly midnight)
The treaty will come into force on the stroke of midnight tonight.
He's gone for a midnight swim.