# -*- coding: utf-8 -*-
# This file is part of convertdate.
# http://github.com/fitnr/convertdate
# Licensed under the MIT license:
# http://opensource.org/licenses/MIT
# Copyright (c) 2016, fitnr <fitnr@fakeisthenewreal>
from math import trunc
from .utils import jwday, monthcalendarhelper
from .gregorian import to_jd as gregorian_to_jd, from_jd as gregorian_from_jd
J0000 = 1721424.5 # Julian date of Gregorian epoch: 0000-01-01
J1970 = 2440587.5 # Julian date at Unix epoch: 1970-01-01
JMJD = 2400000.5 # Epoch of Modified Julian Date system
JULIAN_EPOCH = 1721423.5
J2000 = 2451545.0 # Julian day of J2000 epoch
JULIANCENTURY = 36525.0 # Days in Julian century
HAVE_30_DAYS = (4, 6, 9, 11)
HAVE_31_DAYS = (1, 3, 5, 7, 8, 10, 12)
def leap(year):
if year % 4 and year > 0:
return 0
else:
return 3
def month_length(year, month):
if month == 2:
daysinmonth = 29 if leap(year) else 28
else:
daysinmonth = 30 if month in HAVE_30_DAYS else 31
return daysinmonth
def legal_date(year, month, day):
'''Check if this is a legal date in the Julian calendar'''
daysinmonth = month_length(year, month)
if not (0 < day <= daysinmonth):
raise ValueError("Month {} doesn't have a day {}".format(month, day))
return True
def from_jd(jd):
'''Calculate Julian calendar date from Julian day'''
jd += 0.5
z = trunc(jd)
a = z
b = a + 1524
c = trunc((b - 122.1) / 365.25)
d = trunc(365.25 * c)
e = trunc((b - d) / 30.6001)
if trunc(e < 14):
month = e - 1
else:
month = e - 13
if trunc(month > 2):
year = c - 4716
else:
year = c - 4715
day = b - d - trunc(30.6001 * e)
return (year, month, day)
def to_jd(year, month, day):
'''Convert to Julian day using astronomical years (0 = 1 BC, -1 = 2 BC)'''
legal_date(year, month, day)
# Algorithm as given in Meeus, Astronomical Algorithms, Chapter 7, page 61
if month <= 2:
year -= 1
month += 12
return (trunc((365.25 * (year + 4716))) + trunc((30.6001 * (month + 1))) + day) - 1524.5
def from_gregorian(year, month, day):
return from_jd(gregorian_to_jd(year, month, day))
def to_gregorian(year, month, day):
return gregorian_from_jd(to_jd(year, month, day))
def monthcalendar(year, month):
start_weekday = jwday(to_jd(year, month, 1))
monthlen = month_length(year, month)
return monthcalendarhelper(start_weekday, monthlen)
