The date the model was published.
The use of “laws” originated prior to science splitting from natural philosophy. There’s an implicit assumption that God as the creator laid down both moral and natural laws, with the theologian concerned with the former and the natural philosopher concerned with the latter.
“Theory” begins to take hold in the late 1700s and, very roughly speaking, is used to describe more complex models. “Law” eventually became nearly archaic, although still used to describe very pithy models (Amdahl’s Law, Gustafson’s Law).
The word “model” is gradually superseding both of them.
People have tried to come up with hard-and-fast rules to distinguish them, but scientists are unruly beasts, and use whatever language suits them in the moment.
