Ab Urbe Condita: The definition of the Empire’s Harmonious Calendar is this, counting from the founding – or, rather, counting from the winter solstice [1] that immediately preceded the founding (which was in the mid-to-late spring) in order that the start of the calendar year should be in a sensible place. And, technically, that year is numbered zero, not one, because discontinuities in the number line of years are annoying.

[1] If you were wondering how this ties into Eliéra’s non-standard what’s-axial-tilt-ness, consider it semantically equal to apodeuteros.