Epoch: Landing = 1 Jan 2100 CE, 00:00 UTC → 0 A.L. Dates before the epoch are shown as B.L. (Before Landing), using the same day/circle/quadrant structure projected backward. 1 A.L. year = 408 days of 30 hours = exactly 510 Earth days (matches the corridor's 1.396-Earth-year orbital period). Quadrants (4 × 102 days) and circles (51 × 8 days) both partition the year independently — circles do not nest inside quadrants.