My son is 8 months old and I am at the end. The night time crying must end permanently. How do I make it so that he knows that playtime is ok when the sun is in the sky, and he is not to be heard at all, under any circumstance, when it is dark?

It is little worrying that your 8mo is still crying at night. Timing of feed is important -- have late 11 pm feed and make your baby sleep. Anyways, this is just enough to keep him silent for next 5 hours. Aleast, it will give you good span of sleep. I have observed that if your baby sleeps during evening time then night do come out nightmares. Avoid or delay evening time nap to adjust your baby in a day and night cycle.