151 lines
3.8 KiB
Python
151 lines
3.8 KiB
Python
# -*- coding: utf-8 -*-
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# This file is part of convertdate.
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# http://github.com/fitnr/convertdate
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# Licensed under the MIT license:
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# http://opensource.org/licenses/MIT
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# Copyright (c) 2016, fitnr <fitnr@fakeisthenewreal>
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from calendar import isleap
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from . import gregorian
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from .utils import floor
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from .data import positivist as data
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'''
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Convert between Gregorian/Julian Day and Comte's Positivist calendar.
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The Positivist calendar has 13 months and one or two festival days.
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Festival days are given as the fourteenth month.
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The Gregorian date 1789-01-01 is Positivist 0001-01-01.
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'''
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# Positivist calendar has 13 28-day months and one festival day
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EPOCH = 2374479.5
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YEAR_EPOCH = 1789
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DAYS_IN_YEAR = 365
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MONTHS = (
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'Moses', 'Homer', 'Aristotle', 'Archimedes',
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'Caesar', 'Saint Paul', 'Charlemagne', 'Dante',
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'Gutenberg', 'Shakespeare', 'Descartes', 'Frederic',
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'Bichat', ''
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)
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def legal_date(year, month, day):
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'''Checks if a given date is a legal positivist date'''
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try:
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assert year >= 1
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assert 0 < month <= 14
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assert 0 < day <= 28
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if month == 14:
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if isleap(year + YEAR_EPOCH - 1):
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assert day <= 2
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else:
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assert day == 1
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except AssertionError:
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raise ValueError("Invalid Positivist date: ({}, {}, {})".format(year, month, day))
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return True
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def to_jd(year, month, day):
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'''Convert a Positivist date to Julian day count.'''
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legal_date(year, month, day)
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gyear = year + YEAR_EPOCH - 1
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return (
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gregorian.EPOCH - 1 + (365 * (gyear - 1)) +
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floor((gyear - 1) / 4) + (-floor((gyear - 1) / 100)) +
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floor((gyear - 1) / 400) + (month - 1) * 28 + day
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)
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def from_jd(jd):
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'''Convert a Julian day count to Positivist date.'''
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try:
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assert jd >= EPOCH
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except AssertionError:
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raise ValueError('Invalid Julian day')
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depoch = floor(jd - 0.5) + 0.5 - gregorian.EPOCH
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quadricent = floor(depoch / gregorian.INTERCALATION_CYCLE_DAYS)
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dqc = depoch % gregorian.INTERCALATION_CYCLE_DAYS
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cent = floor(dqc / gregorian.LEAP_SUPPRESSION_DAYS)
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dcent = dqc % gregorian.LEAP_SUPPRESSION_DAYS
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quad = floor(dcent / gregorian.LEAP_CYCLE_DAYS)
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dquad = dcent % gregorian.LEAP_CYCLE_DAYS
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yindex = floor(dquad / gregorian.YEAR_DAYS)
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year = (
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quadricent * gregorian.INTERCALATION_CYCLE_YEARS +
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cent * gregorian.LEAP_SUPPRESSION_YEARS +
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quad * gregorian.LEAP_CYCLE_YEARS + yindex
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)
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if yindex == 4:
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yearday = 365
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year = year - 1
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else:
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yearday = (
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depoch -
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quadricent * gregorian.INTERCALATION_CYCLE_DAYS -
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cent * gregorian.LEAP_SUPPRESSION_DAYS -
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quad * gregorian.LEAP_CYCLE_DAYS -
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yindex * gregorian.YEAR_DAYS
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)
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month = floor(yearday / 28)
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return (year - YEAR_EPOCH + 2, month + 1, int(yearday - (month * 28)) + 1)
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def from_gregorian(year, month, day):
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return from_jd(gregorian.to_jd(year, month, day))
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def to_gregorian(year, month, day):
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return gregorian.from_jd(to_jd(year, month, day))
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def dayname(year, month, day):
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'''
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Give the name of the month and day for a given date.
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Returns:
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tuple month_name, day_name
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'''
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legal_date(year, month, day)
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yearday = (month - 1) * 28 + day
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if isleap(year + YEAR_EPOCH - 1):
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dname = data.day_names_leap[yearday - 1]
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else:
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dname = data.day_names[yearday - 1]
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return MONTHS[month - 1], dname
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def weekday(day):
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'''
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Gives the weekday (0=Monday) of a positivist month and day.
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Note that the festival month does not have a day.
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'''
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return (day % 7) - 1
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def festival(month, day):
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'''
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Gives the festival day for a month and day.
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Returns None if inapplicable.
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'''
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return data.festivals.get((month, day))
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