# `Calendrical.Calendar.Shifted`

Makes a calendar whose year begins elsewhere in a base calendar's year:
a fiscal year beginning in July, a year counted from Lady Day as the
Old Style did, or any year begun on a day of a calendar of months.

A date of the calendar is a counted month and a day of it, so dates
order by time. A year that begins on the first day of a base month has
the base's months counted from that month; a year that begins within a
base month has a short month 1, from the day it begins on to the end of
that base month, and a short last month, the days of that base month
before it, so a year begun on 25 March has thirteen months, of which
month 1 is 25 to 31 March and month 13 is 1 to 24 March.

The kernel falls out of the base: a date is the base's date relabelled,
a month's length is the base month's, and `shift/6` is the base's
arithmetic on the base date, relabelled.

### Options

* `:base` is the calendar of months the year is cut from, a calendar
  with as many months in every year. The default is
  `Calendrical.Gregorian`.

* `:year_begins` is `{month, day}` of the base calendar the year begins
  on. The default is `{1, 1}`.

* `:year_number` is the base 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.

* `:written_year` is the year a date is written with: `:base`, the base
  calendar's year the day falls in, as a fiscal date is written with the
  Gregorian year, which is the default, or `:label`, the calendar's own
  year, as the Old Style wrote its dates.

* `:weeks` is the rule the calendar's own weeks follow: a keyword list
  with `:first_day`, 1 for Monday to 7 for Sunday, and
  `:min_days_in_first_week`, or `:from_first_day` for weeks counted from
  the first day of the year. The default is Monday and 1.

* `:cldr_calendar_type`, `:era_calendar_type` and `:years_in_cycle` are
  facts for `c:Calendrical.info/0`, each defaulting to the base
  calendar's, and `:parsing_calendar` names the calendar a written date
  is parsed in, the calendar itself by default.

### Examples

    defmodule FiscalFromJuly do
      use Calendrical.Calendar.Shifted, year_begins: {7, 1}, year_number: :ending
    end

    defmodule LadyDay do
      use Calendrical.Calendar.Shifted,
        base: Calendrical.Julian,
        year_begins: {3, 25},
        year_number: :beginning,
        written_year: :label
    end

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