GaianCalendar 0.1.0

Python library for the Gaian Calendar — a perpetual 13-month solar calendar based on ISO week-year arithmetic.

GaianCalendar

A pure-Python library for the Gaian Calendar — a perpetual 13-month solar calendar based on ISO week-year arithmetic.

from gaian_calendar import GaianDate

today = GaianDate.today()
print(today)                    # e.g. "Aquarius 22, 12026 GE"
print(today.day_of_year)        # e.g. 78
print(today.is_leap_year)       # True
print(today.format("WWWW, MMMM d, yyyy GE"))  # "Sunday, Aquarius 22, 12026 GE"

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Status

Pre-release — planning phase. See planning/ for design documents.

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What is the Gaian Calendar?

The Gaian Calendar is a perpetual reform calendar with these properties:

• 13 regular months of exactly 28 days (4 weeks × 7 days), named after zodiac constellations
• 1 intercalary month (Horus, 7 days) in leap years only — years with ISO week 53
• Perpetual: every calendar date always falls on the same weekday, every year
• Year numbering: Gaian year = ISO week-year + 10,000 (so 2026 CE = 12026 GE)
• Zero weekday drift: recurring events stay on the same day of week indefinitely

The 13 months in order: Sagittarius · Capricorn · Aquarius · Pisces · Aries · Taurus · Gemini · Cancer · Leo · Virgo · Libra · Scorpius · Ophiuchus · (Horus in leap years)

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Installation

pip install gaian-calendar

(Not yet published — coming soon)

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Usage

from datetime import date, timedelta
from gaian_calendar import GaianDate, GaianMonth, is_leap_year

# Today
d = GaianDate.today()

# From Gregorian
d = GaianDate.from_gregorian(date(2026, 2, 22))
print(d)                  # "Aquarius 22, 12026 GE"
print(d.to_gregorian())   # 2026-02-22

# Properties
print(d.year)             # 12026
print(d.month)            # 3
print(d.day)              # 22
print(d.month_name)       # "Aquarius"
print(d.month_symbol)     # "♒"
print(d.weekday_name)     # "Sunday"
print(d.weekday_symbol)   # "☉"
print(d.day_of_year)      # 78
print(d.is_leap_year)     # True

# Arithmetic
next_week = d + timedelta(weeks=1)
yesterday = d - timedelta(days=1)
delta = d - GaianDate(12026, 1, 1)   # timedelta

# Parsing
d = GaianDate.parse("Aquarius 22, 12026")
d = GaianDate.parse("12026-03-22")
d = GaianDate.parse("3/22/12026")

# Formatting
d.format("MMMM d, yyyy GE")          # "Aquarius 22, 12026 GE"
d.format("MMM* DDD")                 # "♒ 078"
d.format("yyyy-MM-dd")               # "12026-03-22"
d.format("ddd")                      # "22nd"

# Leap year check
is_leap_year(12026)    # True
is_leap_year(12025)    # False

# Month info
from gaian_calendar import GaianMonth
m = GaianMonth.AQUARIUS
print(m.symbol)    # "♒"
print(m.element)   # "Air"

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Similar Libraries

This library is modeled after:

• hijridate — Islamic Hijri calendar
• pyluach — Hebrew calendar

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License

MIT