type error = [ | `Does_not_exist| `Invalid_year of int| `Invalid_month of int
]exception Error_exn of errorConstructors
val make : year:int -> month:int -> (t, error) Stdlib.resultval make_exn : year:int -> month:int -> tAccessors
val year_month : t -> int * intComparison
val equal : t -> t -> boolval compare : t -> t -> intArithmetic
val add : ?years:int -> ?months:int -> t -> tval sub : ?years:int -> ?months:int -> t -> tval diff_months : t -> t -> intPretty-printing
val pp_iso8601 : Stdlib.Format.formatter -> t -> unitval to_iso8601 : t -> stringParsing
val of_iso8601 : string -> (t, string) Stdlib.resultval of_iso8601_exn : string -> t