Saturdays are busy every second. The people taking long lunch hours are rushing, people with the rest of the day off are as slow as snails, and people are awake and somewhat alert. This is the worst time to shop. Rush hour, though, is a great time. People who want to beat the traffic have left, people who are staying at the mall are eating dinner, and people driving home just want to get the hell home.
Every single store has a lull in business, except restaurants.
At around six, people notice the lull, and hurry to finish their meals. Also, soccer moms go shopping after rush hour, and after their family is fed. Night shoppers are generally window shoppers who have to count the atoms that are in each dust bunny in the mall. They have eaten, the mall doesn't close for a while, and they have all the time in the world to piss you off. Also, this is the time kids come for the thrills that the malls offer.