# Module Time

    module Time: sig .. end

A module for representing absolute points in time, independent of time zone.

    module Ofday: sig .. end

    module Span: sig .. end

    module Zone: module type of Zone  with type t = Zone.t

    type t = Time_internal.T.t

A fully qualified point in time, independent of timezone.

    val get_sexp_zone : unit -> Zone.t

Sexp conversions use the local timezone by default. This can be overridden by calling `set_sexp_zone`.

    val set_sexp_zone : Zone.t -> unit

    include Hashable_binable

    include Comparable_binable

    include Robustly_comparable

    include Floatable

    include Pretty_printer.S

    include Stringable

The `{to,of}_string` functions in `Time` will produce times with time zone indications, but are generous in what they will read in. String/Sexp.t representations without time zone indications are assumed to be in the machine's local zone.

##### values

Unlike `Time_ns`, this module purposely omits `max_value` and `min_value`: 1. They produce unintuitive corner cases because most people's mental models of time do not include +/- infinity as concrete values 2. In practice, when people ask for these values, it is for questionable uses, e.g., as null values to use in place of explicit options.

    val epoch : t

midnight, Jan 1, 1970 in UTC

###### Basic operations on times

    val add : t -> Span.t -> t

`add t s` adds the span `s` to time `t` and returns the resulting time.

NOTE: adding spans as a means of adding days is not accurate, and may run into trouble due to shifts in daylight savings time, float arithmetic issues, and leap seconds. See the comment at the top of Zone.mli for a more complete discussion of some of the issues of time-keeping. For spans that cross date boundaries, use date functions instead.

    val sub : t -> Span.t -> t

`sub t s` subtracts the span `s` from time `t` and returns the resulting time. See important note for `add`.

    val diff : t -> t -> Span.t

`diff t1 t2` returns time `t1` minus time `t2`.

    val abs_diff : t -> t -> Span.t

`abs_diff t1 t2` returns the absolute span of time `t1` minus time `t2`.

###### Comparisons

    val is_earlier : t -> than:t -> bool

`is_earlier` and `is_later` are like using `<.`, but easier to read.

    val is_later : t -> than:t -> bool

###### Constants

###### Conversions

All these conversion functions use the current time zone. Unless marked _utc, in which case they use Universal Coordinated Time

    val of_date_ofday : Date0.t -> Ofday.t -> zone:Zone.t -> t

    val to_date_ofday : t -> zone:Zone.t -> Date0.t * Ofday.t

    val to_date : t -> zone:Zone.t -> Date0.t

    val to_ofday : t -> zone:Zone.t -> Ofday.t

    val of_date_ofday_precise : Date0.t ->
           Ofday.t ->
           zone:Zone.t ->
           [ `Never of t | `Once of t | `Twice of t * t ]

Because timezone offsets change throughout the year (clocks go forward or back) some local times can occur twice or not at all. In the case that they occur twice, this function gives ``Twice` with both occurrences in order; if they do not occur at all, this function gives ``Never` with the time at which the local clock skips over the desired time of day.

Note that this is really only intended to work with DST transitions and not unusual or dramatic changes, like the calendar change in 1752 (run "cal 9 1752" in a shell to see). In particular it makes the assumption that midnight of each day is unambiguous.

Most callers should use `Time.of_date_ofday` rather than this function. In the ``Twice` and ``Never` cases, `Time.of_date_ofday` will return reasonable times for most uses.

    val convert : from_tz:Zone.t ->
           to_tz:Zone.t -> Date0.t -> Ofday.t -> Date0.t * Ofday.t

    val utc_offset : t -> zone:Zone.t -> Span.t

###### Other string conversions

    val to_filename_string : t -> zone:Zone.t -> string

`to_filename_string t ~zone` converts `t` to string with format YYYY-MM-DD_HH-MM-SS.mmm which is suitable for using in filenames.

    val of_filename_string : string -> zone:Zone.t -> t

`of_filename_string s ~zone` converts `s` that has format YYYY-MM-DD_HH-MM-SS.mmm into time.

    val to_string_fix_proto : [ `Local | `Utc ] -> t -> string

    val of_string_fix_proto : [ `Local | `Utc ] -> string -> t

    val to_string_trimmed : t -> zone:Zone.t -> string

Same as `to_string_abs`, but removes trailing seconds and milliseconds if they are 0

    val to_sec_string : t -> zone:Zone.t -> string

Same as `to_string_abs`, but without milliseconds

    val of_localized_string : zone:Zone.t -> string -> t

`of_localized_string ~zone str` read in the given string assuming that it represents a time in zone and return the appropriate Time.t

    val to_string_abs : t -> zone:Zone.t -> string

`to_string_abs ~zone t` returns a string that represents an absolute time, rather than a local time with an assumed time zone. This string can be round-tripped, even on a machine in a different time zone than the machine that wrote the string.

The string will display the date and of-day of `zone` together with `zone` as an offset from UTC.

`to_string_abs_trimmed` is the same as `to_string_abs`, but drops trailing seconds and milliseconds if they are 0.

Note that the difference between `to_string` and `to_string_abs` is not that one returns an absolute time and one doesn't, but that `to_string_abs` lets you specify the time zone, while `to_string` takes it to be the local time zone.

    val to_string_abs_trimmed : t -> zone:Zone.t -> string

    val of_string_abs : string -> t

`of_string_abs s` is like `of_string`, but demands that `s` indicate the timezone the time is expressed in.

    val t_of_sexp_abs : Core_kernel.Std.Sexp.t -> t

`t_of_sexp_abs sexp` as `t_of_sexp`, but demands that `sexp` indicate the timezone the time is expressed in.

###### Miscellaneous

    val now : unit -> t

Returns the current time.

    val pause : Span.t -> unit

`pause span` sleeps for span time.

    val interruptible_pause : Span.t -> [ `Ok | `Remaining of Span.t ]

`interruptible_pause span` sleeps for span time unless interrupted (e.g. by delivery of a signal), in which case the remaining unslept portion of time is returned.

    val pause_forever : unit -> Core_kernel.Std.never_returns

`pause_forever` sleeps indefinitely.

    val occurrence : [ `First_after_or_at | `Last_before_or_at ] ->
           t -> ofday:Ofday.t -> zone:Zone.t -> t

`occurrence side time ~ofday ~zone` returns a `Time.t` that is the occurrence of ofday (in the given `zone`) that is the latest occurrence (<=) `time` or the earliest occurrence (>=) `time`, according to `side`.

NOTE: If the given time converted to wall clock time in the given zone is equal to ofday then the t returned will be equal to the t given.

    val format : t -> string -> string

`format t fmt` formats the given time according to fmt, which follows the formatting rules given in 'man strftime'. The time is output in the local timezone.

          %Y - year (4 digits)
          %y - year (2 digits)
          %m - month
          %d - day
          %H - hour
          %M - minute
          %S - second

a common choice would be: %Y-%m-%d %H:%M:%S

    val to_epoch : t -> float

`to_epoch t` returns the number of seconds since Jan 1, 1970 00:00:00 in UTC

    val next_multiple : ?can_equal_after:bool ->
           base:t -> after:t -> interval:Span.t -> unit -> t

    module Stable: sig .. end

    val t_of_sexp : Sexplib.Sexp.t -> t

    val sexp_of_t : t -> Sexplib.Sexp.t

    val bin_t : t Core_kernel.Std.Bin_prot.Type_class.t

    val bin_read_t : t Core_kernel.Std.Bin_prot.Read.reader

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

    val bin_reader_t : t Core_kernel.Std.Bin_prot.Type_class.reader

    val bin_size_t : t Core_kernel.Std.Bin_prot.Size.sizer

    val bin_write_t : t Core_kernel.Std.Bin_prot.Write.writer

    val bin_writer_t : t Core_kernel.Std.Bin_prot.Type_class.writer

Sexp conversions use the local timezone by default. This can be overridden by calling `set_sexp_zone`.
The `{to,of}_string` functions in `Time` will produce times with time zone indications, but are generous in what they will read in. String/Sexp.t representations without time zone indications are assumed to be in the machine's local zone.

##### values

Unlike `Time_ns`, this module purposely omits `max_value` and `min_value`: 1. They produce unintuitive corner cases because most people's mental models of time do not include +/- infinity as concrete values 2. In practice, when people ask for these values, it is for questionable uses, e.g., as null values to use in place of explicit options.
midnight, Jan 1, 1970 in UTC

###### Basic operations on times

`add t s` adds the span `s` to time `t` and returns the resulting time.

NOTE: adding spans as a means of adding days is not accurate, and may run into trouble due to shifts in daylight savings time, float arithmetic issues, and leap seconds. See the comment at the top of Zone.mli for a more complete discussion of some of the issues of time-keeping. For spans that cross date boundaries, use date functions instead.
`sub t s` subtracts the span `s` from time `t` and returns the resulting time. See important note for `add`.
`diff t1 t2` returns time `t1` minus time `t2`.
`abs_diff t1 t2` returns the absolute span of time `t1` minus time `t2`.

###### Comparisons

`is_earlier` and `is_later` are like using `<.`, but easier to read.

###### Constants

###### Conversions

All these conversion functions use the current time zone. Unless marked _utc, in which case they use Universal Coordinated Time
Because timezone offsets change throughout the year (clocks go forward or back) some local times can occur twice or not at all. In the case that they occur twice, this function gives ``Twice` with both occurrences in order; if they do not occur at all, this function gives ``Never` with the time at which the local clock skips over the desired time of day.

Note that this is really only intended to work with DST transitions and not unusual or dramatic changes, like the calendar change in 1752 (run "cal 9 1752" in a shell to see). In particular it makes the assumption that midnight of each day is unambiguous.

Most callers should use `Time.of_date_ofday` rather than this function. In the ``Twice` and ``Never` cases, `Time.of_date_ofday` will return reasonable times for most uses.

###### Other string conversions

`to_filename_string t ~zone` converts `t` to string with format YYYY-MM-DD_HH-MM-SS.mmm which is suitable for using in filenames.
`of_filename_string s ~zone` converts `s` that has format YYYY-MM-DD_HH-MM-SS.mmm into time.
Same as `to_string_abs`, but removes trailing seconds and milliseconds if they are 0
Same as `to_string_abs`, but without milliseconds
`of_localized_string ~zone str` read in the given string assuming that it represents a time in zone and return the appropriate Time.t
`to_string_abs ~zone t` returns a string that represents an absolute time, rather than a local time with an assumed time zone. This string can be round-tripped, even on a machine in a different time zone than the machine that wrote the string.

The string will display the date and of-day of `zone` together with `zone` as an offset from UTC.

`to_string_abs_trimmed` is the same as `to_string_abs`, but drops trailing seconds and milliseconds if they are 0.

Note that the difference between `to_string` and `to_string_abs` is not that one returns an absolute time and one doesn't, but that `to_string_abs` lets you specify the time zone, while `to_string` takes it to be the local time zone.
`of_string_abs s` is like `of_string`, but demands that `s` indicate the timezone the time is expressed in.
`t_of_sexp_abs sexp` as `t_of_sexp`, but demands that `sexp` indicate the timezone the time is expressed in.

###### Miscellaneous

`pause span` sleeps for span time.
`interruptible_pause span` sleeps for span time unless interrupted (e.g. by delivery of a signal), in which case the remaining unslept portion of time is returned.
`pause_forever` sleeps indefinitely.
`occurrence side time ~ofday ~zone` returns a `Time.t` that is the occurrence of ofday (in the given `zone`) that is the latest occurrence (<=) `time` or the earliest occurrence (>=) `time`, according to `side`.

NOTE: If the given time converted to wall clock time in the given zone is equal to ofday then the t returned will be equal to the t given.
`format t fmt` formats the given time according to fmt, which follows the formatting rules given in 'man strftime'. The time is output in the local timezone.

          %Y - year (4 digits)
          %y - year (2 digits)
          %m - month
          %d - day
          %H - hour
          %M - minute
          %S - second

a common choice would be: %Y-%m-%d %H:%M:%S
`to_epoch t` returns the number of seconds since Jan 1, 1970 00:00:00 in UTC
default is `false`
Provides a sexp representation that is independent of the time zone of the machine writing it.