sig
type t = UTC | Local | UTC_Plus of int
val current : unit -> Time_Zone.t
val change : Time_Zone.t -> unit
val gap : Time_Zone.t -> Time_Zone.t -> int
val from_gmt : unit -> int
val to_gmt : unit -> int
val is_dst : unit -> bool
val hour_of_dst : unit -> int
val on : ('a -> 'b) -> Time_Zone.t -> 'a -> 'b
end