Can i go in an R rated movie?

ok so at the beginning of this month i went the movies and it was about 5 pm and i wanted to buy tickets for me and my cousin (we are 16) to watch UNDERWORLD and they said we needed ID so we just left the theather, but later that night it was about 8 pm and we tried buying the tickets again and they didnt ask for ID or the our age . so what im trying to ask is that they can sell us the movie tickets if we go to the movies at 8 or 9 pm because i want to go watch a rated R movie with a friend we are both 16 and i was wondering if they would sell us the tickets? we want to see Miss March lol