Just to throw in my $0.02, during the night, starches drain from the leaves into the root system, and during the day the starches are brought back up into the leaves, so if you harvest after night time, before daylight when the starches come back up, the end result may be a less harsh smoke, as starches in leaves contribute to the harshness. So yeah, during the day = starch and sugars accumulated in leaves, night = starch and sugars accumulated in roots. There is a thing you can do to test it called an iodine test, where you stain the leaves with iodine, as it will turn the starches black so you can see how much starch is in them. This is a picture of an iodine test done on Geranium leaves, the leaf on the left was harvested during a light period and is dark because the starch is stained by the iodine, the leaf on the right was harvested after an extended dark period without being exposed to light, and it light green because there is no starch for the iodine to stain. Personally, I wouldn't want to be smoking all that starch, so my advice would be harvest before the sun comes up if at all possible