A reconstructive solar-lunar calendar employing fixed Halakim integers (1 day = 25,920 Halakim) is analyzed for long-term drift. Year lengths are restricted to 354, 355, or 384 days. A 19-year cycle places seven leap years; a 342-year shift maintains alignment. Verification of a 7,252-year ledger confirms perfect adjacency of every 355-day trim year to a 384-day leap year (1,409/1,409), 19-year groups of 6,939 or 6,940 days, and a mean year length of 365.2368days. The same 25,920 integer organizes the day, calendar cycles, and—under a defined spatial scaling factor of approximately 1.014764—an exact integer light-second of 11,977,113,600 inches and a polar rotation of exactly 60,800inches per Halakim. Weekday and year-length columns map algorithmically onto diatonic intervals and triads. The framework eliminates floating-point drift in calendrical and related coordinate calculations. Implications for orbital mechanics, numerical simulation stability, and high-energy computational methods are discussed as properties of the integer arithmetic rather than as new empirical constants. The system is fully deterministic once the 4026 BCE anchor and constants are fixed.