year ::= full-year | simple-year ; ±E*CCYY | CCYY | YY full-year ::= short-year | long-year ; ±E*CCYY | CCYY basic-year ::= short-year | simple-year ; CCYY | YY simple-year ::= to-doublezero ; YY = 00..99 short-year ::= simple-century simple-year ; CCYY = 0000..9999 long-year ::= positive-year | negative-year ; ±E*CCYY positive-year ::= plus long-century simple-year ; +E*CCYY negative-year ::= minus long-century simple-year ; -E*CCYY century ::= simple-century | long-century ; E*CC simple-century ::= to-doublezero ; CC = 00..99 long-century ::= (1-6)*DIGIT simple-century ; C+ = ... triad-of-year ::= to-four ; Q = 1..4 month-of-year ::= to-twelve ; MM = 01..12 month-of-triad ::= to-three ; M = 1..3 month-of-quart ::= to-three ; M = 1..3 day-of-year ::= to-threesixtysix ; DDD = 001..365/366