package orsetto

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A library of assorted structured data interchange languages

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dune-project
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Authors

  1. J
    james woodyatt <jhw@conjury.org>

Maintainers

  1. J
    james woodyatt <jhw@conjury.org>

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doc/orsetto.cf/Cf_gregorian/index.html

Module Cf_gregorian

Civil dates in the proleptic Gregorian calendar.

Overview

This module implements a record type inhabited by proleptic Gregorian calendar dates. It also provides related functions and types to facilitate conversion to and from various formats for data interchange.

Days, weeks, and months are numbered according to ISO 8601. Days of the month are represented by integers from 1 to 31. Months of the year are represented by integers from 1 to 12. Days of the week are represented by integers from 1 to 7, where 1 is Monday and 7 is Sunday. Days of the year are numbered from 1 to 366, where only leap years contain day number 366. Weeks of the year are numbered from 1 to 53.

Additional, an ancillary private type is also provided here to facilitate conversions between a useful subset of dates and their corresponding Chronological Julian Day (CJD) numbers. These functions are useful for adjustments of dates by intervals measured in integral numbers of days. The first Chronological Julian Day, numbered zero, was 24 Nov 4714 BCE.

Types
type date = private
  1. | Date of {
    1. year : int64;
      (*

      Astonomical year number.

      *)
    2. month : int;
      (*

      Months from January = 1 to December = 12

      *)
    3. day : int;
      (*

      Days 1 to 31.

      *)
    }

The private type inhabited by dates in a useful subset of the proleptic Gregorian calendar.

type cjd =
  1. | CJD of int

The type inhabited by Chronological Julian Day numbers, which correspond to a useful subset of dates in the Gregorian calendar, including those dates that are accepted by the Internet time stamp format (RFC 3339).

Functions
val create : year:int64 -> month:int -> day:int -> date

Use create ~year ~month ~day to create a date according to the values of ~year, ~month and ~day. Raises Invalid_argument if the month or day values are not valid for year in the proleptic Gregorian calendar.

val is_valid : year:int64 -> month:int -> day:int -> bool

Using is_valid ~year ~month ~day returns true if year, month and day arguments specify a valid proleptic Gregorian date.

val day_of_week : date -> int

Use day_of_week d to compute the day of the week on which d occurs. Days of the week are numbered according to ISO 8601, i.e. from 1 to 7, starting on Monday and ending on Sunday.

val day_of_year : date -> int

Use day_of_year day to compute the ordinal day of the year on which d occurs according to ISO 8601, i.e. from 1 to 366.

val week_number : date -> int64 * int

Use week_number d to compute the year and week number in which d occurs. Weeks are numbered according to ISO 8601, i.e. from 1 to 53.

val to_cjd : date -> cjd

to_cjd d computes the Chronological Julian Day number for d.

Gregorian dates between 12 Aug 2937947 BCE and 27 Feb 2935093 CE inclusive are convertible to Chronological Julian Day numbers on platforms where the Ocaml integer is a 31-bit integer. Accordingly, Failure is raised if the Chronological Julian Day corresponding to the date is outside the range that can be represented with an integer.

val in_cjd_range : date -> bool

Using is_cjd_range d returns true if d is within the range of dates that can be represented by a Chronological Julian Day (CJD) number.

val of_cjd : cjd -> date

of_cjd cjd returns the Gregorian date that corresponds to cjd.