To avoid confusion, the correct designation for twelve o'clock is 12 noon or 12 midnight.
From the en.wikipedia.org
On the hour there is a presentation of statues of the Apostles at the doorways above the clock, with all twelve presented at noon.
From the en.wikipedia.org
The astronomical day was shifted from noon, twelve hours after midnight, to midnight effective 1 January 1925 by a resolution of the newly formed International Astronomical Union.