operation,purpose,rule,example
Same-side BC subtraction,Measures a distance within BC chronology,Earlier BC label − later BC label,1936 − 1446 = 490
Uniform BC translation,"Moves every selected coordinate by the same amount, preserving order",x − 860,1936/1876/1816 → 1076/1016/956
Local Exodus-centered complement,"Pairs selected BC coordinates across the center, reversing order",R₁₄₄₆(x) = 2892 − x,1936 ↔ 956; 1876 ↔ 1016; 1816 ↔ 1076
Formal repository Mirror,Generates counterparts under declared cross-axis coordinate/display and phase rules,Protocol appropriate to the selected single-date or paired-seasonal state,Not the operation used for the BC-only 980-year construction
Civil BC–AD elapsed span,Measures elapsed years after cross-axis endpoints have been specified,BC + AD − 1,Not applied to these BC-only differences