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https://github.com/hnthap/lunar.h

Lunar Calendar CLI written in C
https://github.com/hnthap/lunar.h

c c99 chinese-calendar cli cli-app lunar-calendar lunisolar-calendar vietnamese-calendar

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Lunar Calendar CLI written in C

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README 

        
# Gregorian-Lunar (Lunisolar) Calendars Converter



Converting from Gregorian calendar to Vietnamese Lunar calendar (add `-tz 8` for Chinese Lunar calendar), and from Lunar calendar to Gregorian.



Astronomical algorithms from [Ho Ngoc Duc's work](https://www.informatik.uni-leipzig.de/~duc/amlich/calrules.html).



I re-wrote the algorithms in C to implement an easy-to-use CLI application. This requires a compiler that supports C99 or later.



## Compilation



In my case, I use gcc 8.3.0, but any other compilers that support C99 may work just fine (have not tested yet).



```bash

# Change directory to the directory containing this README

# then run this



gcc -Wpedantic -g src/lunar.c -o lunar

```



## Arguments



* `-tz`: Time zone in hours, e.g. `-tz 7` (default) is for UTC+07:00, `-tz 8` is for UTC+08:00.

* `-y`: Year, e.g. `-y 2024` is the year 2024.

* `-m`: Month from 1 to 12, e.g. `-m 7` is July (Gregorian calendar) or the 7th month (Lunar calendar).

* `-d`: Day of month, from 1 to 31, e.g. `-d 21` is the 21st day of the month.

* `-l`: (Lunar calendar only) Whether the month is leap. When `-l` does not present, the month is set as not leap, otherwise leap.

* `-lms`: (Lunar calendar only) Show the month's size ("大" and "小").

* `-lm`: (Only when displaying Lunar calendar) Display the date in Lunar calendar in "modern notation", e.g.

  * 2024.06.16: The **16th** day of the **6th** month (**non-leap**) of the Lunar year whose New Year falls in the Gregorian year **2024**.

  * 2025.06+.01: The **1st** day of the **6th** month (**leap**) of the Lunar year whose New Year falls in the Gregorian year **2025**.

* `-r`: Converting the date specified by `-y`, `-m`, `-l` and `-d` in Lunar calendar to Gregorian.

* `-ly`: Print the first days of all months in the Lunar year specified by `-y` along with their equivalent Gregorian date.



## Usage



Convert date from Gregorian calendar to Lunar calendar:



```bash

./lunar 

# Output: "甲辰年六月十六日"

# Explain: Today in Lunar calendar.

# Set "-tz 8" for Chinese calendar.



./lunar -lms

# Output: "甲辰年六月（小）十六日"

# Explain: Today in Lunar calendar -- showing month size.

# Set "-tz 8" for Chinese calendar.



./lunar -lm

# Output: "2024.06.16" 

# Explain: Today in Lunar calendar - modern notation.

# Set "-tz 8" for Chinese calendar.



./lunar -y 2025 -m 7 -d 30

# Output: "乙巳年閏六月初六日" 

# Explain: 2025-07-30 in Gregorian calendar to Lunar.

# Set "-tz 8" for Chinese calendar.



./lunar -y 2025 -m 7 -d 30 -lm

# Output: "2025.06+.06"

# Explain: 2025-07-30 in Gregorian calendar to Lunar - modern notation.

# Set "-tz 8" for Chinese calendar.

```



Convert date from Lunar calendar to Gregorian calendar:



```bash

./lunar -r -y 2025 -m 6 -l -d 6

# Output: 2025.07.30

# Explain: Lunar date 2025.06+.06 is Gregorian date 2025.07.30 in time zone UTC+07:00 (Vietnamese calendar).

# Set "-tz 8" for Chinese calendar.

```



List first days of all months in a Lunar year with their equivalent Gregorian dates:



```bash

./lunar -ly -y 2025            

# Output:

# Lunar   Gregorian

# 2025.01.01      2025.01.29

# 2025.02.01      2025.02.28

# 2025.03.01      2025.03.29

# 2025.04.01      2025.04.28

# 2025.05.01      2025.05.27

# 2025.06.01      2025.06.25

# 2025.06+.01     2025.07.25

# 2025.07.01      2025.08.23

# 2025.08.01      2025.09.22

# 2025.09.01      2025.10.21

# 2025.10.01      2025.11.20

# 2025.11.01      2025.12.20

# 2025.12.01      2026.01.19

```