The affect of night light on menstrual cycles

I just had the shortest cycle I've had while charting, and I suspect the shortest for a while before that as well. I ovulated on day 19, a solid 7 days before my previous earliest ovulation and my cycle ended on day 31. What a sudden change! This has gotten me speculating on what might have made the difference. At first I thought that nothing had changed, but then I did some sleuthing and found a few articles on the effect of light at night on the menstrual cycle.

• There's good evidence that light effects sleep. And I'm sure we all know this intuitively! Artificial lights at night make it harder to fall asleep and stay asleep.  
• The body produces more melatonin, a hormone, when it is dark. Melatonin helps regulate other hormones in the body, and effects menstruation.
• There's some evidence that using light from day 13-17 while sleeping in a dark room the rest of the cycle promotes regular cycles.

Now, I haven't purposefully lit my room on days 13-17, but I did put up heavy curtains a little over a month ago. Right away I noticed that I was sleeping better. I noticed a longer luteal phase in my previous cycle. Then this cycle, I ovulated much earlier and again had a longer luteal phase. Perhaps the light has something to do with it? I'm hoping the pattern continues!