175 lines
4.1 KiB
Python
175 lines
4.1 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 math import trunc
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from . import gregorian
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from .utils import jwday, monthcalendarhelper
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EPOCH = 347995.5
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HEBREW_YEAR_OFFSET = 3760
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# Hebrew months
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NISAN = 1
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IYYAR = 2
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SIVAN = 3
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TAMMUZ = 4
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AV = 5
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ELUL = 6
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TISHRI = 7
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HESHVAN = 8
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KISLEV = 9
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TEVETH = 10
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SHEVAT = 11
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ADAR = 12
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VEADAR = 13
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def leap(year):
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# Is a given Hebrew year a leap year ?
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return (((year * 7) + 1) % 19) < 7
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def year_months(year):
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'''How many months are there in a Hebrew year (12 = normal, 13 = leap)'''
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if leap(year):
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return 13
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else:
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return 12
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def delay_1(year):
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'''Test for delay of start of new year and to avoid'''
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# Sunday, Wednesday, and Friday as start of the new year.
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months = trunc(((235 * year) - 234) / 19)
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parts = 12084 + (13753 * months)
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day = trunc((months * 29) + parts / 25920)
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if ((3 * (day + 1)) % 7) < 3:
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day += 1
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return day
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def delay_2(year):
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'''Check for delay in start of new year due to length of adjacent years'''
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last = delay_1(year - 1)
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present = delay_1(year)
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next_ = delay_1(year + 1)
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if next_ - present == 356:
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return 2
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elif present - last == 382:
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return 1
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else:
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return 0
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def year_days(year):
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'''How many days are in a Hebrew year ?'''
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return to_jd(year + 1, 7, 1) - to_jd(year, 7, 1)
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def month_days(year, month):
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'''How many days are in a given month of a given year'''
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if month > 13:
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raise ValueError("Incorrect month index")
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# First of all, dispose of fixed-length 29 day months
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if month in (IYYAR, TAMMUZ, ELUL, TEVETH, VEADAR):
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return 29
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# If it's not a leap year, Adar has 29 days
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if month == ADAR and not leap(year):
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return 29
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# If it's Heshvan, days depend on length of year
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if month == HESHVAN and (year_days(year) % 10) != 5:
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return 29
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# Similarly, Kislev varies with the length of year
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if month == KISLEV and (year_days(year) % 10) == 3:
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return 29
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# Nope, it's a 30 day month
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return 30
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def to_jd(year, month, day):
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months = year_months(year)
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jd = EPOCH + delay_1(year) + delay_2(year) + day + 1
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if month < 7:
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for mon in range(7, months + 1):
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jd += month_days(year, mon)
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for mon in range(1, month):
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jd += month_days(year, mon)
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else:
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for mon in range(7, month):
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jd += month_days(year, mon)
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return int(jd) + 0.5
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def from_jd(jd):
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jd = trunc(jd) + 0.5
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count = trunc(((jd - EPOCH) * 98496.0) / 35975351.0)
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year = count - 1
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i = count
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while jd >= to_jd(i, 7, 1):
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i += 1
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year += 1
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if jd < to_jd(year, 1, 1):
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first = 7
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else:
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first = 1
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month = i = first
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while jd > to_jd(year, i, month_days(year, i)):
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i += 1
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month += 1
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day = int(jd - to_jd(year, month, 1)) + 1
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return (year, month, day)
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def to_jd_gregorianyear(gregorianyear, hebrew_month, hebrew_day):
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# gregorian year is either 3760 or 3761 years less than hebrew year
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# we'll first try 3760 if conversion to gregorian isn't the same
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# year that was passed to this method, then it must be 3761.
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for y in (gregorianyear + HEBREW_YEAR_OFFSET, gregorianyear + HEBREW_YEAR_OFFSET + 1):
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jd = to_jd(y, hebrew_month, hebrew_day)
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gd = gregorian.from_jd(jd)
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if gd[0] == gregorianyear:
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break
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else:
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gd = None
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if not gd: # should never occur, but just incase...
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raise ValueError("Could not determine gregorian year")
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# tuple: (y, m, d)
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return (gd[0], gd[1], gd[2])
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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 monthcalendar(year, month):
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start_weekday = jwday(to_jd(year, month, 1))
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monthlen = month_days(year, month)
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return monthcalendarhelper(start_weekday, monthlen)
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