I went outside and found frozen eggs. Really! First time too. I now understand why birds don't lay their eggs in the winter. Never really thought about it, really.
We found one of our broody's nests on the patio. There were twenty or so frozen eggs, they're nearly unbreakable. My brother and I had fun launching them into the air, the never broke.
I just found a stash of frozen eggs that a single girl had hidden (they were all the same size and shade of green). Little rascal! They're just going in the compost heap here since I don't know how old they are.
I had two last week when our temps were down in the teens. I checked when I closed the pop door at about 7pm but evidently somebody (probably the same hen) laid after that two nights in a row. I found each egg the following morning hard as a rock with a cracked shell.