12 o'clock
12 o'clock usually refers the time as shown on a 12-hour clock, either noon - 12 o'clock at daytime - or midnight - 12 o'clock at nighttime.
12 o'clock may also refer to:

12-hour clock, a time convention in which the 24 hours of the day are divided into two periods
Noon, 12 o'clock in the daytime, as opposed to midnight
Midnight, the transition time from one day to the next
The corresponding clock position, straight ahead or directly above
12 O'Clock (film), a 1958 Bollywood film
12 'O' Clock (film) a 2020 Bollywood film
12 O'Clock (rapper), a Wu-Tang Clan affiliate and MC
12:00 (Loona EP), 2020
Twelve O'Clock Point, a community in Quinte West, Ontario, Canada
"12 O'Clock" (in two parts), a song by Vangelis from Heaven and Hell

See also
Twelve O'Clock High, a 1949 American war film about aircrews in the United States Army's Eighth Air Force
Twelve O'clock Knob (Roanoke County, Virginia), a mountain located in southwestern Roanoke County, Virginia