why this day?

This layer is a composition of three separate systems rather than one synthetic ancient day: a restrained astral layer, a Roman civic-calendar layer, and an Attic reconstruction layer.

Roman labels are computed directly from Kalends, Nones, and Ides. Greek labels are shown only as Attic reconstructions and keep visible uncertainty. Astral notes use real sky-state categories but remain observational rather than predictive.

Confidence is shown because the Roman civic layer is firmer than the Greek reconstructed layer, and because omission is better than false precision.