Wildsky is right.
I actually keep track, and they don't lay at the same time every day. It starts in the morning, gets a bit later, a bit later, until finally they lay towards the end of the day, then skip a day and start over.
It would be possible to have a hen with an exact 24 hour cycle that would lay at the same time every day. None of mine do. It's more like 25 to 27 hours, depending on the hen.