They charge all day, then switch on the LED when it get far into dusk. I picked up a few of these at the local Dollar Tree. You can pop the tops off, giving you the cell, battery, and white LED on something like a hockey puck. Taping 3 together into a triangle, letting charge all day, then testing in a tent at night: they put out enough light to read by when in the gear loft or in a wide-mesh bag, and ran pretty much all night (as far as I can tell)
So for $3.00, one can get a tent light that'll last at least for years and is very lightweight. If one goes bad, you still have two working. How will candle lanterns compete with that, when there's no chance of fire or accidentally burning your fingers?
Next, I plan to disassemble one to see if I can rig the solar cell to the stem and the LED over my cyclocomputer on some sort of stiff yet bendable wire...let's see if there's enough slack wire inside to make it easy.
You can get solar tent lights on Ebay, but they run about 10X more expensive than my triangle light, and look a lot heavier.