129 lines
3.0 KiB
Python
129 lines
3.0 KiB
Python
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# -*- 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, monthrange
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from .utils import floor, monthcalendarhelper, jwday
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EPOCH = 1721425.5
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INTERCALATION_CYCLE_YEARS = 400
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INTERCALATION_CYCLE_DAYS = 146097
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LEAP_SUPPRESSION_YEARS = 100
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LEAP_SUPPRESSION_DAYS = 36524
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LEAP_CYCLE_YEARS = 4
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LEAP_CYCLE_DAYS = 1461
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YEAR_DAYS = 365
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HAVE_30_DAYS = (4, 6, 9, 11)
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HAVE_31_DAYS = (1, 3, 5, 7, 8, 10, 12)
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def legal_date(year, month, day):
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'''Check if this is a legal date in the Gregorian calendar'''
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if month == 2:
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daysinmonth = 29 if isleap(year) else 28
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else:
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daysinmonth = 30 if month in HAVE_30_DAYS else 31
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if not (0 < day <= daysinmonth):
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raise ValueError("Month {} doesn't have a day {}".format(month, day))
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return True
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def to_jd2(year, month, day):
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'''Gregorian to Julian Day Count for years between 1801-2099'''
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# http://quasar.as.utexas.edu/BillInfo/JulianDatesG.html
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legal_date(year, month, day)
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if month <= 2:
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year = year - 1
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month = month + 12
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a = floor(year / 100)
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b = floor(a / 4)
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c = 2 - a + b
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e = floor(365.25 * (year + 4716))
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f = floor(30.6001 * (month + 1))
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return c + day + e + f - 1524.5
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def to_jd(year, month, day):
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legal_date(year, month, day)
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if month <= 2:
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leap_adj = 0
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elif isleap(year):
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leap_adj = -1
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else:
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leap_adj = -2
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return (
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EPOCH - 1 + (YEAR_DAYS * (year - 1)) +
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floor((year - 1) / LEAP_CYCLE_YEARS) +
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(-floor((year - 1) / LEAP_SUPPRESSION_YEARS)) +
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floor((year - 1) / INTERCALATION_CYCLE_YEARS) +
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floor((((367 * month) - 362) / 12) + leap_adj + day)
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)
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def from_jd(jd):
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'''Return Gregorian date in a (Y, M, D) tuple'''
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wjd = floor(jd - 0.5) + 0.5
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depoch = wjd - EPOCH
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quadricent = floor(depoch / INTERCALATION_CYCLE_DAYS)
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dqc = depoch % INTERCALATION_CYCLE_DAYS
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cent = floor(dqc / LEAP_SUPPRESSION_DAYS)
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dcent = dqc % LEAP_SUPPRESSION_DAYS
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quad = floor(dcent / LEAP_CYCLE_DAYS)
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dquad = dcent % LEAP_CYCLE_DAYS
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yindex = floor(dquad / YEAR_DAYS)
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year = (
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quadricent * INTERCALATION_CYCLE_YEARS +
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cent * LEAP_SUPPRESSION_YEARS +
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quad * LEAP_CYCLE_YEARS + yindex
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)
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if not (cent == 4 or yindex == 4):
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year += 1
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yearday = wjd - to_jd(year, 1, 1)
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leap = isleap(year)
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if yearday < 58 + leap:
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leap_adj = 0
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elif leap:
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leap_adj = 1
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else:
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leap_adj = 2
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month = floor((((yearday + leap_adj) * 12) + 373) / 367)
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day = int(wjd - to_jd(year, month, 1)) + 1
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return (year, month, day)
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def month_length(year, month):
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return monthrange(year, month)[1]
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def monthcalendar(year, month):
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start_weekday = jwday(to_jd(year, month, 1))
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monthlen = month_length(year, month)
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return monthcalendarhelper(start_weekday, monthlen)
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