I agree, no set time. Also expect times to vary for most of your hens. There are various triggers that tells a hen when to release a yolk to start its journey through her internal egg making factory. One of those is when the last egg was laid, the next yolk is usually released a few minutes after she lays one. Since it normally takes about 25 hours on average for an egg to travel through her internal factory the next egg can come a little later each day. But 25 hours is just an average, some can be quite a bit quicker. So it is possible she may lay her egg about the same time each day. Or it may take longer than 25 hours so there is more of a daily gap.