Ok, I just learned a few days ago that I could go back and do lights that I had missed while i was out of town with no internet. So I hurried and did that to at least get all the lights across the top, not knowing when the calendar might "expire" plus harder to find animals as time goes on. But now I have at least those, how do I get back to the last days/lights. I was at 5 so I went ahead and tried going to 1 to see if I could then go to 31, but that didn't work. If I'm going to have to cycle through them all, many for probably the whole 12 hrs, then I may as well just give up and save the coins.

You can go back to any light to get all 8 lights lit. You just close the door when you have 8 spots and then go back to another day.

You can go back a day at a time to get the ones you missed or didn't complete. Click the calendar, then click the option to go back. Keep going back a day at a time until you get to the ones you want to do.
 
  The central light is day 1, then even numbers to the left and odd to the right.

Unfortunately you can't advance until you've spotted all 8, or the 12 hours goes by and the door closes. But it goes faster if you spot the 8, although that does take time and resources.

You don't have to spot the ones you've unlocked again.

Kelly thanks. That's what I feared, I'll never get back to the last 8 or so days before the wildlife gardens run out

If you don't complete the calendar this year, then I believe you can still put it in storage and complete it next year. Obviously there will be a new calendar next year (and I think you can only have one in your garden at a time), but you can keep it until winter wildlife is plentiful again.

Ben that would be nice!