"""The dates module implements classes for representing and
manipulating several date types.
Contents
--------
* :class:`Rounding`
* :class:`BaseDate`
* :class:`CalendarDateMixin`
* :class:`JulianDay`
* :class:`GregorianDate`
* :class:`HebrewDate`
Note
----
All instances of the classes in this module should be treated as read
only. No attributes should be changed once they're created.
"""
import abc
from datetime import date
from numbers import Number
from enum import Enum, auto
from pyluach import utils
from pyluach import gematria
[docs]class Rounding(Enum):
"""Enumerator to provide options for rounding Hebrew dates.
This provides constants to use as arguments for functions. It
should not be instantiated.
Attributes
----------
PREVIOUS_DAY
If the day is the 30th and the month only has 29 days, round to
the 29th of the month.
NEXT_DAY
If the day is the 30th and the month only has 29 days, round to
the 1st of the next month.
EXCEPTION
If the day is the 30th and the month only has 29 days, raise a
ValueError.
"""
PREVIOUS_DAY = auto()
NEXT_DAY = auto()
EXCEPTION = auto()
[docs]class BaseDate(abc.ABC):
"""BaseDate is a base class for all date types.
It provides the following arithmetic and comparison operators
common to all child date types.
=================== =================================================
Operation Result
=================== =================================================
d2 = date1 + int New date ``int`` days after date1
d2 = date1 - int New date ``int`` days before date1
int = date1 - date2 Positive integer equal to the duration from date1
to date2
date1 > date2 True if date1 occurs later than date2
date1 < date2 True if date1 occurs earlier than date2
date1 == date2 True if date1 occurs on the same day as date2
date1 != date2 True if ``date1 == date2`` is False
=================== =================================================
Any subclass of ``BaseDate`` can be compared to and diffed with any other
subclass date.
"""
@property
@abc.abstractmethod
def jd(self):
"""Return julian day number.
Returns
-------
float
The Julian day number at midnight (as ``n.5``).
"""
[docs] @abc.abstractmethod
def to_heb(self):
"""Return Hebrew Date.
Returns
-------
HebrewDate
"""
def __hash__(self):
return hash(repr(self))
def __add__(self, other):
try:
return JulianDay(self.jd + other)._to_x(self)
except TypeError:
return NotImplemented
def __sub__(self, other):
try:
if isinstance(other, Number):
return JulianDay(self.jd - other)._to_x(self)
return int(abs(self.jd - other.jd))
except (AttributeError, TypeError):
return NotImplemented
def __eq__(self, other):
try:
return self.jd == other.jd
except AttributeError:
return NotImplemented
def __ne__(self, other):
try:
return self.jd != other.jd
except AttributeError:
return NotImplemented
def __lt__(self, other):
try:
return self.jd < other.jd
except AttributeError:
return NotImplemented
def __gt__(self, other):
try:
return self.jd > other.jd
except AttributeError:
return NotImplemented
def __le__(self, other):
try:
return self.jd <= other.jd
except AttributeError:
return NotImplemented
def __ge__(self, other):
try:
return self.jd >= other.jd
except AttributeError:
return NotImplemented
[docs] def weekday(self):
"""Return day of week as an integer.
Returns
-------
int
An integer representing the day of the week with Sunday as 1
through Saturday as 7.
"""
return int(self.jd+.5+1) % 7 + 1
[docs] def isoweekday(self):
"""Return the day of the week corresponding to the iso standard.
Returns
-------
int
An integer representing the day of the week where Monday
is 1 and and Sunday is 7.
"""
weekday = self.weekday()
if weekday == 1:
return 7
return weekday - 1
[docs] def shabbos(self):
"""Return the Shabbos on or following the date.
Returns
-------
JulianDay, GregorianDate, or HebrewDate
`self` if the date is Shabbos or else the following Shabbos as
the same date type as called from.
Examples
--------
>>> heb_date = HebrewDate(5781, 3, 29)
>>> greg_date = heb_date.to_greg()
>>> heb_date.shabbos()
HebrewDate(5781, 4, 2)
>>> greg_date.shabbos()
GregorianDate(2021, 6, 12)
"""
return self + (7 - self.weekday())
def _day_of_holiday(self, israel, hebrew=False):
"""Return the day of the holiday.
Parameters
----------
israel : bool, optional
hebrew : bool, optional
Returns
-------
str
"""
name = utils._festival_string(self, israel)
if name is not None:
holiday = utils._Days(name)
if holiday is utils._Days.SHAVUOS and israel:
return ''
first_day = utils._first_day_of_holiday(holiday)
if first_day:
year = self.to_heb().year
day = HebrewDate(year, *first_day) - self + 1
if hebrew:
day = gematria._num_to_str(day)
return str(day)
return ''
[docs] def fast_day(self, hebrew=False):
"""Return name of fast day of date.
Parameters
----------
hebrew : bool, optional
``True`` if you want the fast day name in Hebrew letters. Default
is ``False``, which returns the name transliterated into English.
Returns
-------
str or None
The name of the fast day or ``None`` if the date is not
a fast day.
"""
return utils._fast_day_string(self, hebrew)
[docs] def festival(
self,
israel=False,
hebrew=False,
include_working_days=True,
prefix_day=False
):
"""Return name of Jewish festival of date.
This method will return all major and minor religous
Jewish holidays not including fast days.
Parameters
----------
israel : bool, optional
``True`` if you want the holidays according to the Israel
schedule. Defaults to ``False``.
hebrew : bool, optional
``True`` if you want the festival name in Hebrew letters. Default
is ``False``, which returns the name transliterated into English.
include_working_days : bool, optional
``True`` to include festival days on which melacha (work) is
allowed; ie. Pesach Sheni, Chol Hamoed, etc.
Default is ``True``.
prefix_day : bool, optional
``True`` to prefix multi day festivals with the day of the
festival. Default is ``False``.
Returns
-------
str or None
The name of the festival or ``None`` if the given date is not
a Jewish festival.
Examples
--------
>>> pesach = HebrewDate(2023, 1, 15)
>>> pesach.festival(prefix_day=True)
'1 Pesach'
>>> pesach.festival(hebrew=True, prefix_day=True)
'א׳ פסח'
>>> shavuos = HebrewDate(5783, 3, 6)
>>> shavuos.festival(israel=True, prefix_day=True)
'Shavuos'
"""
name = utils._festival_string(
self, israel, hebrew, include_working_days
)
if prefix_day and name is not None:
day = self._day_of_holiday(israel=israel, hebrew=hebrew)
if day:
return f'{day} {name}'
return name
[docs] def holiday(self, israel=False, hebrew=False, prefix_day=False):
"""Return name of Jewish holiday of the date.
The holidays include the major and minor religious Jewish
holidays including fast days.
Parameters
----------
israel : bool, optional
``True`` if you want the holidays according to the Israel
schedule. Defaults to ``False``.
hebrew : bool, optional
``True`` if you want the holiday name in Hebrew letters. Default is
``False``, which returns the name transliterated into English.
prefix_day : bool, optional
``True`` to prefix multi day holidays with the day of the
holiday. Default is ``False``.
Returns
-------
str or None
The name of the holiday or ``None`` if the given date is not
a Jewish holiday.
Examples
--------
>>> pesach = HebrewDate(2023, 1, 15)
>>> pesach.holiday(prefix_day=True)
'1 Pesach'
>>> pesach.holiday(hebrew=True, prefix_day=True)
'א׳ פסח'
>>> taanis_esther = HebrewDate(5783, 12, 13)
>>> taanis_esther.holiday(prefix_day=True)
'Taanis Esther'
"""
return (
self.fast_day(hebrew=hebrew)
or self.festival(israel, hebrew, prefix_day=prefix_day)
)
[docs]class CalendarDateMixin:
"""CalendarDateMixin is a mixin for Hebrew and Gregorian dates.
Parameters
----------
year : int
month : int
day : int
Attributes
----------
year : int
month : int
day : int
jd : float
The equivalent Julian day at midnight.
"""
def __init__(self, year, month, day, jd=None):
self.year = year
self.month = month
self.day = day
self._jd = jd
def __repr__(self):
class_name = self.__class__.__name__
return f'{class_name}({self.year}, {self.month}, {self.day})'
def __str__(self):
return f'{self.year:04d}-{self.month:02d}-{self.day:02d}'
def __iter__(self):
yield self.year
yield self.month
yield self.day
[docs] def tuple(self):
"""Return date as tuple.
Returns
-------
tuple of ints
A tuple of ints in the form ``(year, month, day)``.
"""
return (self.year, self.month, self.day)
[docs] def dict(self):
"""Return the date as a dictionary.
Returns
-------
dict
A dictionary in the form
``{'year': int, 'month': int, 'day': int}``.
"""
return {'year': self.year, 'month': self.month, 'day': self.day}
[docs] def replace(self, year=None, month=None, day=None):
"""Return new date with new values for the specified field.
Parameters
----------
year : int, optional
month: int, optional
day : int, optional
Returns
-------
CalendarDateMixin
Any date that inherits from CalendarDateMixin
(``GregorianDate``, ````HebrewDate``).
Raises
ValueError
Raises a ``ValueError`` if the new date does not exist.
"""
if year is None:
year = self.year
if month is None:
month = self.month
if day is None:
day = self.day
return type(self)(year, month, day)
[docs]class JulianDay(BaseDate):
"""A JulianDay object represents a Julian Day at midnight.
Parameters
----------
day : float or int
The julian day. Note that Julian days start at noon so day
number 10 is represented as 9.5 which is day 10 at midnight.
Attributes
----------
day : float
The Julian Day Number at midnight (as *n*.5)
"""
def __init__(self, day):
if day-int(day) < .5:
self.day = int(day) - .5
else:
self.day = int(day) + .5
def __repr__(self):
return f'JulianDay({self.day})'
def __str__(self):
return str(self.day)
@property
def jd(self):
"""Return julian day.
Returns
-------
float
"""
return self.day
[docs] @staticmethod
def from_pydate(pydate):
"""Return a `JulianDay` from a python date object.
Parameters
----------
pydate : datetime.date
A python standard library ``datetime.date`` instance
Returns
-------
JulianDay
"""
return GregorianDate.from_pydate(pydate).to_jd()
[docs] @staticmethod
def today():
"""Return instance of current Julian day from timestamp.
Extends the built-in ``datetime.date.today()``.
Returns
-------
JulianDay
A JulianDay instance representing the current Julian day from
the timestamp.
Warning
-------
Julian Days change at noon, but pyluach treats them as if they
change at midnight, so at midnight this method will return
``JulianDay(n.5)`` until the following midnight when it will
return ``JulianDay(n.5 + 1)``.
"""
return GregorianDate.today().to_jd()
[docs] def to_greg(self):
"""Convert JulianDay to a Gregorian Date.
Returns
-------
GregorianDate
The equivalent Gregorian date instance.
Notes
-----
This method uses the Fliegel-Van Flandern algorithm.
"""
jd = int(self.day + .5)
L = jd + 68569
n = 4*L // 146097
L = L - (146097*n + 3) // 4
i = (4000 * (L+1)) // 1461001
L = L - ((1461*i) // 4) + 31
j = (80*L) // 2447
day = L - 2447*j // 80
L = j // 11
month = j + 2 - 12*L
year = 100 * (n-49) + i + L
if year < 1:
year -= 1
return GregorianDate(year, month, day, self.day)
[docs] def to_heb(self):
""" Convert to a Hebrew date.
Returns
-------
HebrewDate
The equivalent Hebrew date instance.
"""
if self.day <= 347997:
raise ValueError('Date is before creation')
jd = int(self.day + .5) # Try to account for half day
jd -= 347997
year = int(jd//365) + 2 # try that to debug early years
first_day = utils._elapsed_days(year)
while first_day > jd:
year -= 1
first_day = utils._elapsed_days(year)
months = utils._monthslist(year)
days_remaining = jd - first_day
for month in months:
if days_remaining >= utils._month_length(year, month):
days_remaining -= utils._month_length(year, month)
else:
return HebrewDate(year, month, days_remaining + 1, self.day)
def _to_x(self, type_):
"""Return a date object of the given type."""
if isinstance(type_, GregorianDate):
return self.to_greg()
if isinstance(type_, HebrewDate):
return self.to_heb()
if isinstance(type_, JulianDay):
return self
raise TypeError(
'This method has not been implemented with that type.'
)
[docs] def to_pydate(self):
"""Convert to a datetime.date object.
Returns
-------
datetime.date
A standard library ``datetime.date`` instance.
"""
return self.to_greg().to_pydate()
[docs]class GregorianDate(BaseDate, CalendarDateMixin):
"""A GregorianDate object represents a Gregorian date (year, month, day).
This is an idealized date with the current Gregorian calendar
infinitely extended in both directions.
Parameters
----------
year : int
month : int
day : int
jd : float, optional
This parameter should not be assigned manually.
Attributes
----------
year : int
month : int
day : int
Warnings
--------
Although B.C.E. dates are allowed, they should be treated as
approximations as they may return inconsistent results when converting
between date types and using arithmetic and comparison operators!
"""
def __init__(self, year, month, day, jd=None):
"""Initialize a GregorianDate.
This initializer extends the CalendarDateMixin initializer
adding in date validation specific to Gregorian dates.
"""
if month < 1 or month > 12:
raise ValueError(f'{str(month)} is an invalid month.')
monthlength = self._monthlength(year, month)
if day < 1 or day > monthlength:
raise ValueError(f'Given month has {monthlength} days.')
super().__init__(year, month, day, jd)
def __format__(self, fmt):
return self.strftime(fmt)
[docs] def strftime(self, fmt):
"""Return formatted date.
Wraps :py:meth:`datetime.date.strftime` method and uses the same
format options.
Parameters
----------
fmt : str
The format string.
Returns
-------
str
"""
return self.to_pydate().strftime(fmt)
@property
def jd(self):
"""Return the corresponding Julian day number.
Returns
-------
float
The Julian day number at midnight.
"""
if self._jd is None:
year = self.year
month = self.month
day = self.day
if year < 0:
year += 1
if month < 3:
year -= 1
month += 12
month += 1
a = year // 100
b = 2 - a + a//4
self._jd = (
int(365.25*year) + int(30.6001*month) + b + day + 1720994.5
)
return self._jd
[docs] @classmethod
def from_pydate(cls, pydate):
"""Return a `GregorianDate` instance from a python date object.
Parameters
----------
pydate : datetime.date
A python standard library ``datetime.date`` instance.
Returns
-------
GregorianDate
"""
return cls(*pydate.timetuple()[:3])
[docs] @staticmethod
def today():
"""Return a GregorianDate instance for the current day.
This static method wraps the Python standard library's
date.today() method to get the date from the timestamp.
Returns
-------
GregorianDate
The current Gregorian date from the computer's timestamp.
"""
return GregorianDate.from_pydate(date.today())
@staticmethod
def _is_leap(year):
"""Return True if year of date is a leap year, otherwise False."""
if year < 0:
year += 1
if (year % 4 == 0) and not (year % 100 == 0 and year % 400 != 0):
return True
return False
[docs] def is_leap(self):
"""Return if the date is in a leap year
Returns
-------
bool
True if the date is in a leap year, False otherwise.
"""
return self._is_leap(self.year)
@classmethod
def _monthlength(cls, year, month):
if month in [1, 3, 5, 7, 8, 10, 12]:
return 31
if month == 2:
if cls._is_leap(year):
return 29
return 28
return 30
[docs] def to_jd(self):
"""Convert to a Julian day.
Returns
-------
JulianDay
The equivalent JulianDay instance.
"""
return JulianDay(self.jd)
[docs] def to_heb(self):
"""Convert to Hebrew date.
Returns
-------
HebrewDate
The equivalent HebrewDate instance.
"""
return self.to_jd().to_heb()
[docs] def to_pydate(self):
"""Convert to a standard library date.
Returns
-------
datetime.date
The equivalent datetime.date instance.
"""
return date(*self.tuple())
[docs]class HebrewDate(BaseDate, CalendarDateMixin):
"""A class for manipulating Hebrew dates.
The following format options are available similar to strftime:
====== ======= ===========================================================
Format Example Meaning
====== ======= ===========================================================
%a Sun Weekday as locale's abbreviated name
%A Sunday Weekday as locale's full name
%w 1 Weekday as decimal number 1-7 Sunday-Shabbos
%d 07 Day of the month as a 0-padded 2 digit decimal number
%-d 7 Day of the month as a decimal number
%B Iyar Month name transliterated into English
%m 02 Month as a 0-padded 2 digit decimal number
%-m 2 Month as a decimal number
%y 82, 01 Year without century as a zero-padded decimal number
%Y 5782 Year as a decimal number
%*a א׳ Weekday as a Hebrew numeral
%*A ראשון Weekday name in Hebrew
%*d ז׳, ט״ז Day of month as Hebrew numeral
%*-d א, טו Day of month without gershayim
%*B אייר Name of month in Hebrew
%*y תשפ״ב Year in Hebrew numerals without the thousands place
%*Y ה'תשפ״ב Year in Hebrew numerals with the thousands place
%% % A literal '%' character
====== ======= ===========================================================
Example
-------
>>> date = HebrewDate(5783, 1, 15)
>>> f'Today is {date:%a - %*-d %*B, %*y}'
'Today is Thu - טו אייר, תשפ"ג'
Parameters
----------
year : int
The Hebrew year.
month : int
The Hebrew month starting with Nissan as 1 (and Tishrei as 7). If
there is a second Adar in the year it is has a value of 13.
day : int
The Hebrew day of the month.
jd : float, optional
This parameter should not be assigned manually.
Attributes
----------
year : int
month : int
The Hebrew month starting with Nissan as 1 (and Tishrei as 7).
If there is a second Adar it has a value of 13.
day : int
The day of the month.
Raises
------
ValueError
If the year is less than 1, if the month is less than 1 or greater
than the last month, or if the day does not exist in the month a
``ValueError`` will be raised.
"""
def __init__(self, year, month, day, jd=None):
"""Initialize a HebrewDate instance.
This initializer extends the CalendarDateMixin adding validation
specific to hebrew dates.
"""
if year < 1:
raise ValueError('Year must be >= 1.')
if month < 1 or month > 13:
raise ValueError(f'{month} is an invalid month.')
if (not utils._is_leap(year)) and month == 13:
raise ValueError(f'{year} is not a leap year')
monthlength = utils._month_length(year, month)
if day < 1 or day > monthlength:
raise ValueError(f'Given month has {monthlength} days.')
super().__init__(year, month, day, jd)
def __format__(self, fmt):
new = []
i = 0
while i < len(fmt):
if fmt[i] != '%':
new.append(fmt[i])
else:
i += 1
try:
curr = fmt[i]
except IndexError as e:
raise ValueError(
'Format string cannot end with single "%".'
) from e
if curr == '%':
new.append('%')
elif curr == '*':
i += 1
try:
curr = fmt[i]
except IndexError as e:
raise ValueError(
'Format string cannot end with "%*".'
) from e
if curr == '-':
i += 1
try:
curr = fmt[i]
except IndexError as e:
raise ValueError(
'Format string cannot end with "%*-"'
) from e
if curr == 'd':
new.append(self.hebrew_day(False))
else:
raise ValueError('Invalid format string.')
elif curr == 'a':
new.append(gematria._num_to_str(self.weekday()))
elif curr == 'A':
new.append(utils.WEEKDAYS[self.weekday()])
elif curr == 'd':
new.append(self.hebrew_day())
elif curr == 'B':
new.append(self.month_name(True))
elif curr.casefold() == 'y':
new.append(self.hebrew_year(curr == 'Y'))
else:
raise ValueError('Invalid format string.')
elif curr == '-':
i += 1
try:
curr = fmt[i]
except IndexError as e:
raise ValueError(
'Format string cannot end with "%-"'
) from e
if curr == 'd':
new.append(str(self.day))
elif curr == 'm':
new.append(str(self.month))
else:
raise ValueError('Invalid format string.')
else:
if curr.casefold() == 'a':
new.append(self.to_pydate().strftime(f'%{curr}'))
elif curr == 'w':
new.append(str(self.weekday()))
elif curr == 'd':
new.append(format(self.day, '02d'))
elif curr == 'B':
new.append(self.month_name(False))
elif curr == 'm':
new.append(format(self.month, '02d'))
elif curr.casefold() == 'y':
new.append(date(self.year, 1, 1).strftime(f'%{curr}'))
else:
raise ValueError('Invalid format string.')
i += 1
return ''.join(new)
@property
def jd(self):
"""Return the corresponding Julian day number.
Returns
-------
float
The Julian day number at midnight.
"""
if self._jd is None:
months = utils._monthslist(self.year)
jd = utils._elapsed_days(self.year)
for m in months:
if m != self.month:
jd += utils._month_length(self.year, m)
else:
self._jd = jd + (self.day-1) + 347996.5
return self._jd
[docs] @staticmethod
def from_pydate(pydate):
"""Return a `HebrewDate` from a python date object.
Parameters
----------
pydate : datetime.date
A python standard library ``datetime.date`` instance
Returns
-------
HebrewDate
"""
return GregorianDate.from_pydate(pydate).to_heb()
[docs] @staticmethod
def today():
"""Return HebrewDate instance for the current day.
This static method wraps the Python standard library's
``date.today()`` method to get the date from the timestamp.
Returns
-------
HebrewDate
The current Hebrew date from the computer's timestamp.
Warning
-------
Pyluach treats Hebrew dates as if they change at midnight. If it's
after nightfall but before midnight, to get the true Hebrew date do
``HebrewDate.today() + 1``.
"""
return GregorianDate.today().to_heb()
[docs] def to_jd(self):
"""Convert to a Julian day.
Returns
-------
JulianDay
The equivalent JulianDay instance.
"""
return JulianDay(self.jd)
[docs] def to_greg(self):
"""Convert to a Gregorian date.
Returns
-------
GregorianDate
The equivalent GregorianDate instance.
"""
return self.to_jd().to_greg()
[docs] def to_pydate(self):
"""Convert to a standard library date.
Returns
-------
datetime.date
The equivalent datetime.date instance.
"""
return self.to_greg().to_pydate()
[docs] def to_heb(self):
return self
[docs] def month_name(self, hebrew=False):
"""Return the name of the month.
Parameters
----------
hebrew : bool, optional
``True`` if the month name should be in Hebrew characters.
Default is ``False`` which returns the month name
transliterated into English.
Returns
-------
str
"""
return utils._month_name(self.year, self.month, hebrew)
[docs] def hebrew_day(self, withgershayim=True):
"""Return the day of the month in Hebrew letters.
Parameters
----------
withgershayim : bool, optional
Default is ``True`` which includes a geresh with a single
character and gershayim between two characters.
Returns
-------
str
The day of the month in Hebrew letters.
Examples
--------
>>> date = HebrewDate(5782, 3, 6)
>>> date.hebrew_day()
'ו׳'
>>> date.hebrew_day(False)
'ו'
>>> HebrewDate(5783, 12, 14).hebrew_day()
'י״ד'
"""
return gematria._num_to_str(self.day, withgershayim=withgershayim)
[docs] def hebrew_year(self, thousands=False, withgershayim=True):
"""Return the year in Hebrew letters.
Parameters
----------
thousands : bool
``True`` to prefix the year with a letter for the
thousands place, ie. 'ה׳תשפ״א'. Default is ``False``.
withgershayim : bool, optional
Default is ``True`` which includes a geresh after the thousands
place if applicable and a gershayim before the last character
of the year.
Returns
-------
str
"""
return gematria._num_to_str(self.year, thousands, withgershayim)
[docs] def hebrew_date_string(self, thousands=False):
"""Return a Hebrew string representation of the date.
The date is in the form ``f'{day} {month} {year}'``.
Parameters
----------
thousands : bool
``True`` to have the thousands include in the year.
Default is ``False``.
Returns
-------
str
Examples
--------
>>> date = HebrewDate(5781, 9, 25)
>>> date.hebrew_date_string()
'כ״ה כסלו תשפ״א'
>>> date.hebrew_date_string(True)
'כ״ה כסלו ה׳תשפ״א'
"""
day = self.hebrew_day()
month = self.month_name(True)
year = self.hebrew_year(thousands)
return f'{day} {month} {year}'
[docs] def add(
self,
years=0,
months=0,
days=0,
adar1=False,
rounding=Rounding.NEXT_DAY
):
"""Add years, months, and days to date.
Parameters
----------
years : int, optional
The number of years to add. Default is 0.
months : int, optional
The number of months to add. Default is 0.
days : int, optional
The number of days to add. Default is 0.
adar1 : bool, optional
True to return a date in Adar Aleph if `self` is in a regular
Adar and after adding the years it's leap year. Default is
``False`` which will return the date in Adar Beis.
rounding : Rounding, optional
Choose what to do if self is the 30th day of the month, and
there are only 29 days in the destination month.
:obj:`Rounding.NEXT_DAY` to return the first day of the next
month. :obj:`Rounding.PREVIOUS_DAY` to return the last day of
the month. :obj:`Rounding.EXCEPTION` to raise a ValueError.
Default is :obj:`Rounding.NEXT_DAY`.
Returns
-------
HebrewDate
Note
----
This method first adds the `years`. If the starting month is
Adar and the destination year has two Adars, it chooses which
one based on the `adar1` argument, then it adds the `months`. If
the starting day doesn't exist in that month it adjusts it based
on the `rounding` argument, then it adds the `days`.
Examples
--------
>>> date = HebrewDate(5783, 11, 30)
>>> date.add(months=1)
HebrewDate(5783, 1, 1)
>>> date.add(months=1, rounding=Rounding.PREVIOUS_DAY)
HebrewDate(5783, 12, 29)
"""
year = self.year + years
month = self.month
if self.month == 13 and not utils._is_leap(year):
month = 12
elif (
self.month == 12
and not utils._is_leap(self.year)
and utils._is_leap(year)
and not adar1
):
month = 13
if months > 0:
year, month = utils._add_months(year, month, months)
elif months < 0:
year, month = utils._subtract_months(year, month, -months)
if utils._month_length(year, month) < self.day:
date = HebrewDate(year, month, 29)
if rounding is Rounding.EXCEPTION:
raise ValueError(f'{date:%B %Y} has only 29 days.')
if rounding is Rounding.NEXT_DAY:
date += 1
elif not isinstance(rounding, Rounding):
raise TypeError(
'The rounding argument can only be a member of the'
' dates.Rounding enum.'
)
else:
date = HebrewDate(year, month, self.day)
return date + days
[docs] def subtract(
self,
years=0,
months=0,
days=0,
adar1=False,
rounding=Rounding.NEXT_DAY
):
"""Subtract years, months, and days from date.
Parameters
----------
years : int, optional
The number of years to subtract. Default is 0.
months : int, optional
The number of months to subtract. Default is 0.
days : int, optional
The number of days to subtract. Default is 0.
adar1 : bool, optional
True to return a date in Adar Aleph if `self` is in a regular
Adar and the destination year is leap year. Default is
``False`` which will return the date in Adar Beis.
rounding : Rounding, optional
Choose what to do if self is the 30th day of the month, and
there are only 29 days in the destination month.
:obj:`Rounding.NEXT_DAY` to return the first day of the next
month. :obj:`Rounding.PREVIOUS_DAY` to return the last day of
the month. :obj:`Rounding.EXCEPTION` to raise a ValueError.
Default is :obj:`Rounding.NEXT_DAY`.
Returns
-------
HebrewDate
Note
----
This method first subtracts the `years`. If the starting month
is Adar and the destination year has two Adars, it chooses which
one based on the `adar1` argument, then it subtracts the
`months`. If the starting day doesn't exist in that month it
adjusts it based on the `rounding` argument, then it subtracts
the `days`.
"""
return self.add(-years, -months, -days, adar1, rounding)