Style Guide civil-span excerpt

Original SHA256: 2e7993eac77ec119b27bfc9ace67e3d196d21d358a64c536a1dc8f60729e1abb

Examples:

• 4106 − 1406 = 2700;
• 3486 − 1886 = 1600.

5.2 Cross-axis spans

When the span crosses the BC/AD axis, use the repository-standard formula:

BC + AD − 1

Example:

4166 + 4115 − 1 = 8280

5.3 Do not mix operators

Do not apply same-side subtraction to cross-axis spans. Do not apply BC + AD − 1 to same-side spans.

5.4 Civil-year note

The repository uses civil BC/AD reckoning with no year 0. This is why cross-axis spans use BC + AD − 1.

5.5 Audit categories for arithmetic

Every Arithmetic-layer check (within the Unified Revision Pass, or as a standalone Arithmetic Pass under the High-risk split) should cover at least these categories: