I sometimes feed mealworms on the day my chameleons hatch- but the worms have to be the appropriate size. baby meal worms for baby chameleons. My personal preference is to feed an entire meal's worth of whatever species of insect I am offering on a particular day and switch up what I feed every day- just a personal preference to keep things easy for me. The reason I mention- no harm comes from feeding a full day's ration of mealworms (10 or whatever) in one go, rather than 2 worms every day or whatever. But whatever your preference.
As far as time of day- I haven't ever found that it really matters. I feed mine all kinds of times depending on my schedule from first thing in the morning to late in the evening before lights out. Digestion slows at night while the lizard sleeps and picks up again the next day when the lizard warms up again- the food is still in there for digestion the next day, it doesn't get pooped out undigested or something. Again, just my personal preference, but I don't think a wild chameleon would turn down a feeding opportunity late in the day either.