im confused on saying 7:20 in spanish

2 answers

PM? Son las siete y veinte de la noche.

AM? Son las siete y veinte de la mañana

http://www.spanishspanish.com/time/clock_web.html If you want to hear is spoken
I only use

Son las siete y veinte.

It is very unusual to use AM or PM coloquially (because you see if it is morning or evening time).