Doce en punto. (twelve on the dot)
mediodia
You can get the point across several ways. Primarily, you can say "Son las doce". For noon, you can say "mediodía". For midnight, say "medianoche".
Son las nueve
Son las ocho en punto
Son las ocho menos cinco.
Nuestra casa. A las ocho.
Las tres de la madrugada
12'o clock in midday is pm
It is short for "of the clock".
son las cinco de la tarde/noche
Much as don't is the abbreviation for do not.The abbreviation o'clock is the short for "of the clock".So you could say: "It is now 12 of the clock" instead of: "It is now 12 o'clock"
12 'o clock midnight
Four hundred in Spanish is "cuatrocientos".