dev-nhatty/gregorian-ethiopian-calendar

A python CLI calendar program built for class project # 🗓️ Ethiopian-Aware Calendar A command-line calendar that prints a standard Gregorian (or Julian) year, with the corresponding **Ethiopian calendar date** shown alongside every day — including the correct Ethiopian month spans and the 13th month, Pagume. ``` Gregorian Year: 2024 Ethiopian Years: 2016 - 2017 January Tahsas-Tir |--------------------------------------------------| | Sun | Mon | Tue | Wed | Thu | Fri | Sat | |--------------------------------------------------| | | 1 | 2 | 3 | 4 | 5 | 6 | | | 22 | 23 | 24 | 25 | 26 | 27 | |--------------------------------------------------| | 7 | 8 | 9 | 10 | 11 | 12 | 13 | | 28 | 29 | 30 | 1 | 2 | 3 | 4 | ``` *(top line: Gregorian date, bottom line: Ethiopian date)* ## Why The Ethiopian calendar runs roughly 7–8 years behind the Gregorian calendar and has 13 months (12 of 30 days, plus a short 5- or 6-day month, Pagume). This tool lets you look up the Ethiopian date for any day in a Gregorian or Julian year, month-by-month, from the command line. ## How it works Dates are converted through a **Julian Day Number (JDN)** — a single running count of days used as a common intermediate format between calendar systems. The flow is: ``` Gregorian/Julian date → JDN → Ethiopian date ``` The Gregorian/Julian → JDN formulas are standard astronomical conversions. The JDN → Ethiopian conversion uses a fixed epoch offset (1723856) and a 4-year/1461-day cycle to account for the Ethiopian leap year pattern. **Correctness is checked against known reference dates** in the test suite — specifically, Ethiopian New Year (1 Meskerem) is documented to fall on September 11 in the Gregorian calendar, or September 12 in the year immediately before a Gregorian leap year. All four spot-checked years match. ## Usage **Non-interactive (recommended for scripting/quick lookups):** ```bash python ethiopian_calendar.py 2024 python ethiopian_calendar.py 1750 --calendar J python ethiopian_calendar.py 1750 -c J ` …