Utils for converting between date formats and calculating holidays
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README.rst

convertdate

The convertdate package was originally developed as “Python Date Utils” by Phil Schwartz. It had been significantly updated and expanded.

Available calendars:

  • Bahai
  • French Republican
  • Gregorian
  • Hebrew
  • Indian Civil
  • Islamic
  • Julian
  • Mayan
  • Persian
  • Positivist
  • Mayan
  • ISO
  • Ordinal (day of year)
  • Dublin day count
  • Julian day count

The holidays module also provides some useful holiday-calculation, with a focus on North American and Jewish holidays.

Installing

pip install convertdate

Or download the package and run python setup.py install.

Using

from convertdate import french_republican
from convertdate import hebrew

french_republican.from_gregorian(2014, 10, 31)
# (223, 2, 1, 9)

hebrew.from_gregorian(2014, 10, 31)
# (5775, 8, 7)

Note that in some calendar systems, the day begins at sundown. Convertdate gives the conversion for noon of the day in question.

Each module includes a monthcalendar function, which will generate a calender-like nested list for a year and month (each list of dates runs from Sunday to Saturday)

hebrew.monthcalendar(5775, 8)
# [
#     [None, None, None, None, None, None, 1],
#     [2, 3, 4, 5, 6, 7, 8],
#     [9, 10, 11, 12, 13, 14, 15],
#     [16, 17, 18, 19, 20, 21, 22],
#     [23, 24, 25, 26, 27, 28, 29]
# ]

julian.monthcalendar(2015, 1)
# [
#    [None, None, None, 1, 2, 3, 4],
#    [5, 6, 7, 8, 9, 10, 11],
#    [12, 13, 14, 15, 16, 17, 18],
#    [19, 20, 21, 22, 23, 24, 25],
#    [26, 27, 28, 29, 30, 31, None]
# ]

Special Options

French Republican

Leap year calculations in the French Republican calendar are a matter of dispute. By default, convertdate calculates leap years using the autumnal equinox. You can also use one of three more systematic methods proposed over the years.

  • Romme, a co-creator of the calendar, proposed leap years in years divisible by four, except for years divisible by 100.
  • Some concordances were drawn up in the 19th century that gave leap years every 4 years, in years that give a remainder of three when divided by four (19, 23, 27, etc...).
  • Von Mädler proposed leap years in years divisible by four, except for years divisible by 128.

You can specify any of these three methods with the method keyword argument in french_republican conversion functions.

from convertdate import french_republican

# Romme's method
french_republican.to_gregorian(20, 1, 1), method='romme')
# (1811, 9, 23)

# continuous method
french_republican.to_gregorian(20, 1, 1), method='continuous')
# (1811, 9, 24)

# von Mädler's method
french_republican.to_gregorian(20, 1, 1), method='madler')
# (1811, 9, 23)

All the conversion methods correctly assign the leap years implemented while calendar was in use (3, 7, 11).

Before the Common Era

For dates before the Common Era (year 1), convertdate uses astronomical notation: 1 BC is recorded as 0, 2 BC is -1, etc. This makes arithmatic much easier at the expense of ignoring custom.

Note that for dates before 4 CE, convertdate uses the proleptic Julian calendar. The Julian Calendar was in use from 45 BC, but before 4 CE the leap year leap year pattern was irregular.

The proleptic Gregorian calendar is used for dates before 1582 CE, the year of the Gregorian calendar reform.

Holidays

North American holidays are the current focus of the holidays module, but pull requests are welcome.

from convertdate import holidays

# For simplicity, functions in the holidays module return a tuple
# In the format (year, month, day)

holidays.new_years(2014)
# (2014, 1, 1)

holidays.memorial_day(2014)
# (2014, 5, 26)

# USA is default
holidays.thanksgiving(2014)
# (2014, 11, 27)

# But there is a Canadian option for some holidays
holidays.thanksgiving(2014, 'canada')
# (2014, 10, 13)

# Mexican national holidays
holidays.natalicio_benito_juarez(2016)
# (2016, 3, 21)

holidays.dia_revolucion(2016)
# (2016, 11, 21)

# Some Jewish holidays are included
holidays.rosh_hashanah(2014)

Utils

Convertdate includes some utilities for manipulating and calculating dates.

from convertdate import utils

# Calculate an arbitrary day of the week
THUR = 3
APRIL = 4

# 3rd Thursday in April
utils.nth_day_of_month(3, THUR, APRIL, 2014)
# (2014, 4, 17)

utils.nth_day_of_month(5, THUR, APRIL, 2014)
# IndexError: No 5th day of month 4

# Use 0 for the first argument to get the last weekday of a month
utils.nth_day_of_month(0, THUR, APRIL, 2014)
# (2014, 4, 24)

Note that when calculating weekdays, convertdate uses the convention of the calendar and time modules: Monday is 0, Sunday is 6.

from convertdate import gregorian

SUN = 6

day = gregorian.to_jd(2014, 4, 17)
nextsunday = utils.next_weekday(SUN, day)

gregorian.from_jd(nextsunday)
# (2014, 4, 20)

Other utility functions:

  • nearest_weekday
  • next_or_current_weekday
  • previous_weekday
  • previous_or_current_weekday