They are (were) still modern humans
All the differences are explainable by technology, not biology. This is a particular peeve of mine when pseudohistorians try to make broad generalizations about former civilizations. The ancient Greeks and Romans were still modern humans. They had calendars and lawyers and legal contracts, however only sundials for daily times of day and wood burning stoves or campfires for cooking (with a few exceptions). They could predict the equinoxes and starts of the seasons. It depends upon what you need the "time" of. If they wanted to evict a squatter on a day of the month, they could do that and did do that. If they were trying to guess when you should show up for the pig roast and time it for when it was done, they'd say something that would translate to us as "evening-ish, because they didn't have gas ovens or watches and cooking times for a whole pig have many variables.
That said, the Romans tended to specify things for "the Kalens" (the beginning of the month, or the "Ides", (the middle of the month, generally somewhere between the 13th and 15th of the month depending upon which month.
