Badger's solution works, but an alternative is to post a link to the data here and let LW take a crack at it. I can fit a wide variety of models in a matter of minutes in R, and wouldn't mind spending an hour or two doing so and writing up the results.
Well, I usually include an export of my Zeo CSV data for anyone to look at (not that anyone apparently has for the earlier bigger melatonin data), and I was going to link the results here in an open thread or something.
Quite a few of us are working on interesting projects; many of those are solo, but some could maybe use some help. So here's the place to ask!