# Module `Timezone`

`include Timezone__.Timezone_intf.Timezone`

`module type Extend_zone = Timezone__.Timezone_intf.Extend_zone`

`include Core_kernel.Core_kernel_private.Time_zone.S with type t = Core_kernel.Time.Zone.t`

`type t`

`= Core_kernel.Time.Zone.t`

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.

`val sexp_of_t : t -> Ppx_sexp_conv_lib.Sexp.t`

`val compare : t -> t -> Core_kernel__.Import.int`

`val input_tz_file : zonename:Core_kernel__.Import.string -> filename:Core_kernel__.Import.string -> t`

`input_tz_file ~zonename ~filename`

read in`filename`

and return`t`

with`name t`

=`zonename`

`val likely_machine_zones : Core_kernel__.Import.string Core_kernel__.Import.list Core_kernel__.Import.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:Core_kernel__.Import.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 name : t -> Core_kernel__.Import.string`

`val original_filename : t -> Core_kernel__.Import.string Core_kernel__.Import.option`

`original_filename t`

return the filename`t`

was loaded from (if any)

`val digest : t -> Core_kernel.Md5.t Core_kernel__.Import.option`

`digest t`

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

`val reset_transition_cache : t -> Core_kernel__.Import.unit`

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.

`module Index : sig ... end`

A time zone index refers to a range of times delimited by DST transitions at one or both ends. Every time belongs to exactly one such range. The times of DST transitions themselves belong to the range for which they are the lower bound.

`val index : t -> Time_in_seconds.t -> Index.t`

Gets the index of a time.

`val index_of_date_and_ofday : t -> Time_in_seconds.Date_and_ofday.t -> Index.t`

`val index_offset_from_utc_exn : t -> Index.t -> Time_in_seconds.Span.t`

Gets the UTC offset of times in a specific range.

This can raise if you use an

`Index.t`

that is out of bounds for this`t`

.

`val index_abbreviation_exn : t -> Index.t -> Core_kernel__.Import.string`

`index_abbreviation_exn t index`

returns the abbreviation name (such as EDT, EST, JST) of given zone`t`

for the range of`index`

. This string conversion is one-way only, and cannot reliably be turned back into a`t`

. This function reads and writes the zone's cached index. Raises if`index`

is out of bounds for`t`

.

`val index_has_prev_clock_shift : t -> Index.t -> Core_kernel__.Import.bool`

Accessors for the DST transitions delimiting the start and end of a range, if any. The

`_exn`

accessors raise if there is no such transition. These accessors are split up to increase performance and improve allocation; they are intended as a low-level back-end for commonly-used time conversion functions. See`Time.Zone`

and`Time_ns.Zone`

for higher-level accessors that return an optional tuple for clock shifts in either direction.

`val index_prev_clock_shift_time_exn : t -> Index.t -> Time_in_seconds.t`

`val index_prev_clock_shift_amount_exn : t -> Index.t -> Time_in_seconds.Span.t`

`val index_has_next_clock_shift : t -> Index.t -> Core_kernel__.Import.bool`

`val index_next_clock_shift_time_exn : t -> Index.t -> Time_in_seconds.t`

`val index_next_clock_shift_amount_exn : t -> Index.t -> Time_in_seconds.Span.t`

`include Extend_zone with type Extend_zone.t := t`

`include Core_kernel.Identifiable.S with type t := t`

`include Bin_prot.Binable.S with type t := t`

`include Bin_prot.Binable.S_only_functions with type t := t`

`val bin_size_t : t Bin_prot.Size.sizer`

`val bin_write_t : t Bin_prot.Write.writer`

`val bin_read_t : t Bin_prot.Read.reader`

`val __bin_read_t__ : (int -> t) Bin_prot.Read.reader`

This function only needs implementation if

`t`

exposed to be a polymorphic variant. Despite what the type reads, this does *not* produce a function after reading; instead it takes the constructor tag (int) before reading and reads the rest of the variant`t`

afterwards.

`val bin_shape_t : Bin_prot.Shape.t`

`val bin_writer_t : t Bin_prot.Type_class.writer`

`val bin_reader_t : t Bin_prot.Type_class.reader`

`val bin_t : t Bin_prot.Type_class.t`

`val hash_fold_t : Base.Hash.state -> t -> Base.Hash.state`

`val hash : t -> Base.Hash.hash_value`

`include Ppx_sexp_conv_lib.Sexpable.S with type t := t`

`val t_of_sexp : Sexplib0.Sexp.t -> t`

`val sexp_of_t : t -> Sexplib0.Sexp.t`

`include Core_kernel.Identifiable.S_common with type t := t`

`val compare : t -> t -> Core_kernel__.Import.int`

`val hash_fold_t : Base.Hash.state -> t -> Base.Hash.state`

`val hash : t -> Base.Hash.hash_value`

`val sexp_of_t : t -> Ppx_sexp_conv_lib.Sexp.t`

`include Core_kernel__.Import.Stringable.S with type t := t`

`include Core_kernel__.Import.Pretty_printer.S with type t := t`

`val pp : Base.Formatter.t -> t -> unit`

`include Core_kernel.Comparable.S_binable with type t := t`

`include Core_kernel__.Comparable_intf.S_common`

`include Base.Comparable.S`

`include Base__.Comparable_intf.Polymorphic_compare`

`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 ~compare: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`

`between t ~low ~high`

means`low <= t <= high`

`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`

`val comparator : (t, comparator_witness) Base.Comparator.comparator`

`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`

`module Replace_polymorphic_compare : Core_kernel__.Comparable_intf.Polymorphic_compare with type t := t`

`include Core_kernel__.Comparable_intf.Map_and_set_binable with type t := t with type comparator_witness := comparator_witness`

`include Core_kernel.Comparator.S with type t := t`

`val comparator : (t, comparator_witness) Core_kernel.Comparator.comparator`

`module Map : Core_kernel.Map.S_binable with type Key.t = t with type Key.comparator_witness = comparator_witness`

`module Set : Core_kernel.Set.S_binable with type Elt.t = t with type Elt.comparator_witness = comparator_witness`

`include Core_kernel.Hashable.S_binable with type t := t`

`val hash_fold_t : Base.Hash.state -> t -> Base.Hash.state`

`val hash : t -> Base.Hash.hash_value`

`val hashable : t Core_kernel.Hashtbl.Hashable.t`

`module Table : Core_kernel.Hashtbl.S_binable with type key = t`

`module Hash_set : Core_kernel.Hash_set.S_binable with type elt = t`

`module Hash_queue : Core_kernel.Hash_queue.S with type key = t`

`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 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.

`module Stable : sig ... end`