We dont really know when our hen started sitting, but i am quite sure 21 days would have passed on Saturday. Though not 100% sure. I am thinking by Wednesday the 21 days will DEFENETLY be over. last week i made an attempt at candling them and all 9 of them looked fertilised, with a large dark mass and only a small air bubble. This is the first time the hen has ever sat on eggs, but she has been really committed and only left them once a day. So, can eggs hatch if passed 21 day? Will she leave them on her own if they dont hatch within a set period of time? What could have happened if they were developing and then just never hatched? It is pretty cold here just now, would that have anything to do with it even though she is sitting and the eggs have always been warm?