# `Calendrical.Calendar.Weeks`

Makes a calendar of whole weeks: a year of 52 or 53 weeks that begins
or ends on a weekday near a day of the Gregorian year, cut into twelve
months of four or five weeks by a pattern, as retail and other fiscal
calendars count them and as the ISO week year does.

A date of the calendar is a month of the pattern and a day of it, so a
month of four weeks has days 1 to 28 and one of five weeks days 1 to
35; a long year's last month holds the fifty-third week.

### Options

* `:pattern` is the weeks in the three months of a quarter, one of
  `[4, 4, 5]`, `[4, 5, 4]` and `[5, 4, 4]`. The default is `[4, 5, 4]`.

* `:year_begins` is the rule the year begins by:
  `{weekday, :on_or_before, {month, day}}`, the weekday on or before a
  day of a Gregorian month, the day being 1 to 7, so the year's first
  week holds that day, or `{weekday, :nearest, {month, 4}}`, the weekday
  nearest the fourth, which is the same rule. The ISO week year begins
  `{:monday, :on_or_before, {1, 4}}`. The default is `{:monday, :on_or_before, {1, 1}}`.

* `:year_ends` is the rule the year ends by, instead of `:year_begins`:
  `{weekday, :on_or_after, {month, day}}`, the weekday on or after a day
  within the last seven days of a Gregorian month, so the year's last
  week holds that day, or `{weekday, :nearest, {month, last_day}}`, the
  weekday nearest the month's last day. The NRF 4-5-4 year ends
  `{:saturday, :nearest, {1, 31}}`.

* `:year_number` is the Gregorian year the year takes its number from:
  `:beginning`, the one it begins in, `:ending`, the one it ends in, or
  `:majority`, the one most of it falls in, which is the default.

* `:cldr_calendar_type` is the CLDR calendar whose data names the
  months and days, `:gregorian` by default.

### Examples

    defmodule Retail do
      use Calendrical.Calendar.Weeks,
        pattern: [4, 5, 4],
        year_ends: {:saturday, :nearest, {1, 31}}
    end

    defmodule WeekYear do
      use Calendrical.Calendar.Weeks, year_begins: {:monday, :on_or_before, {1, 4}}
    end

The calendar is its options: the first day of a year is found from the
rule, a month is the weeks of the pattern before it, and every other
answer follows from those two.

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*Consult [api-reference.md](api-reference.md) for complete listing*