What time is too late to call someone?

Does the person have children? Do you know if the person works the following day? If they have young children do not call after nine. If they have older children it is ok to call before ten. If they do not have children at all, and do not have a morning job the next day go for it. If it is that pressing that you can not wait, just call. There are alot of night owls out there.