package core

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package core
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include module type of struct include Core_kernel.Time.Zone end

User-friendly interface

The type of a time-zone.

bin_io and sexp representations of Zone.t are the name of the zone, and not the full data that is read from disk when Zone.find is called. The full Zone.t is reconstructed on the receiving/reading side by reloading the zone file from disk. Any zone name that is accepted by find is acceptable in the bin_io and sexp representations.

include sig ... end
val input_tz_file : zonename:Base.String.t -> filename:Base.String.t -> t

input_tz_file ~zonename ~filename read in filename and return t with name t = zonename

val name : t -> Base.String.t
val original_filename : t -> Base.String.t Base.Option.t

original_filename t return the filename t was loaded from (if any)

digest t return the MD5 digest of the file the t was created from (if any)

absolute_time_of_relative_time and relative_time_of_absolute_time convert times between absolute (time from epoch in UTC) and relative (shifted according to time zone and daylight savings) forms. These are low level functions not intended for most clients.

Takes a Time.t and returns the next Time.t strictly after it, if any, that the time zone UTC offset changes, and by how much it does so.

As next_clock_shift, but strictly *before* the given time.

val reset_transition_cache : t -> Base.Unit.t

For performance testing only; reset_transition_cache t resets an internal cache in t used to speed up repeated lookups of the same clock shift transition.

include Core_kernel.Identifiable.S with type t := t
include sig ... end
val bin_read_t : t Bin_prot.Read.reader
val __bin_read_t__ : (Base.Int.t -> t) Bin_prot.Read.reader
val bin_reader_t : t Bin_prot.Type_class.reader
val bin_size_t : t Bin_prot.Size.sizer
val bin_write_t : t Bin_prot.Write.writer
val bin_writer_t : t Bin_prot.Type_class.writer
val bin_shape_t : Bin_prot.Shape.t
val t_of_sexp : Sexplib.Sexp.t -> t
include Core_kernel.Identifiable.S_common with type t := t
include sig ... end
val sexp_of_t : t -> Sexplib.Sexp.t
include Base.Stringable.S with type t := t
val of_string : string -> t
val to_string : t -> string
include Base.Pretty_printer.S with type t := t
val pp : Caml.Format.formatter -> t -> unit
include Core_kernel.Comparable.S_binable with type t := t
include Base.Comparable_intf.S with type t := t
include Base.Comparable_intf.Polymorphic_compare with type t := t
include Base.Comparisons.Infix with type t := t
val (>=) : t -> t -> bool
val (<=) : t -> t -> bool
val (=) : t -> t -> bool
val (>) : t -> t -> bool
val (<) : t -> t -> bool
val (<>) : t -> t -> bool
val equal : t -> t -> bool
val compare : t -> t -> int

compare t1 t2 returns 0 if t1 is equal to t2, a negative integer if t1 is less than t2, and a positive integer if t1 is greater than t2.

val min : t -> t -> t
val max : t -> t -> t
val ascending : t -> t -> int

ascending is identical to compare. descending x y = ascending y x. These are intended to be mnemonic when used like List.sort ~cmp:ascending and List.sort ~cmp:descending, since they cause the list to be sorted in ascending or descending order, respectively.

val descending : t -> t -> int
val between : t -> low:t -> high:t -> bool
val clamp_exn : t -> min:t -> max:t -> t

clamp_exn t ~min ~max returns t', the closest value to t such that between t' ~low:min ~high:max is true.

Raises if not (min <= max).

val clamp : t -> min:t -> max:t -> t Base.Or_error.t
include Base.Comparator.S with type t := t
type comparator_witness
include Base.Comparable_intf.Validate with type t := t
val validate_lbound : min:t Base.Maybe_bound.t -> t Base.Validate.check
val validate_ubound : max:t Base.Maybe_bound.t -> t Base.Validate.check
val validate_bound : min:t Base.Maybe_bound.t -> max:t Base.Maybe_bound.t -> t Base.Validate.check
include Core_kernel.Comparator.S with type t := t with type comparator_witness := comparator_witness
include Core_kernel.Hashable.S_binable with type t := t
include sig ... end
val hash_fold_t : Base.Hash.state -> t -> Base.Hash.state
val hash : t -> Base.Hash.hash_value
val find : string -> t option

find name looks up a t by its name and returns it. This also accepts some aliases, including:

  • chi -> America/Chicago
  • nyc -> America/New_York
  • hkg -> Asia/Hong_Kong
  • lon -> Europe/London
  • tyo -> Asia/Tokyo
val find_exn : string -> t
val local : t Core_kernel.Lazy.t

local is the machine's local timezone, as determined from the TZ environment variable or the /etc/localtime file. It is computed from the state of the process environment and on-disk tzdata database at some unspecified moment prior to its first use, so its value may be unpredictable if that state changes during program operation. Arguably, changing the timezone of a running program is a problematic operation anyway -- most people write code assuming the clock doesn't suddenly jump several hours without warning.

Note that any function using this timezone can throw an exception if the TZ environment variable is misconfigured or if the appropriate timezone files can't be found because of the way the box is configured. We don't sprinkle _exn all over all the names in this module because such misconfiguration is quite rare.

val likely_machine_zones : string list Pervasives.ref

likely_machine_zones is a list of zone names that will be searched first when trying to determine the machine zone of a box. Setting this to a likely set of zones for your application will speed the very first use of the local timezone.

val of_utc_offset : hours:int -> t

of_utc_offset offset returns a timezone with a static UTC offset (given in hours).

val utc : t

utc the UTC time zone. Included for convenience

val abbreviation : t -> Core_kernel.Time.t -> string

abbreviation zone t returns t abbreviation name such as EDT, EST, JST of given zone at the time t. This string conversion is one-way only, and cannot reliably be turned back into a t

val initialized_zones : unit -> (string * t) list

initialized_zones () returns a sorted list of time zone names that have been loaded from disk thus far.

Low-level functions

The functions below are lower level and should be used more rarely.

val init : unit -> unit

init () pre-load all available time zones from disk, this function has no effect if it is called multiple times. Time zones will otherwise be loaded at need from the disk on the first call to find/find_exn.

module Stable : sig ... end
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