https://github.com/dor-sketch/hebrew-calendar

A web app that utilizes the Intl.DateTimeFormat API to convert Gregorian dates to Hebrew dates accurately and effortlessly.
https://github.com/dor-sketch/hebrew-calendar

calendar chrome-extension hebrew-calendar hebrew-date intl-dateformat jewish-calendar

Last synced: about 6 hours ago
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A web app that utilizes the Intl.DateTimeFormat API to convert Gregorian dates to Hebrew dates accurately and effortlessly.

• Host: GitHub
• URL: https://github.com/dor-sketch/hebrew-calendar
• Owner: Dor-sketch
• License: mit
• Created: 2024-08-29T13:14:50.000Z (about 1 month ago)
• Default Branch: main
• Last Pushed: 2024-10-03T15:14:44.000Z (2 days ago)
• Last Synced: 2024-10-05T03:06:21.564Z (about 6 hours ago)
• Topics: calendar, chrome-extension, hebrew-calendar, hebrew-date, intl-dateformat, jewish-calendar
• Language: HTML
• Homepage: https://dorpascal.com/hebrew-calendar/he
• Size: 1.85 MB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Hebrew Date Calculation Algorithm

Web deployment: [Hebrew Date Calculator](https://dorpascal.com/hebrew-calendar/he/)

Chrome Extension: [Hebrew Date Calculator](https://chromewebstore.google.com/detail/hebrew-calendar/hibmadldekamhiflhbaflaiafdbigihe)

![alt text](chrome-preview.png)

The code uses JavaScript's `Intl.DateTimeFormat` API to convert Gregorian dates to Hebrew dates. Here's a breakdown of how it works:

1. **Intl.DateTimeFormat Initialization:**

   ```javascript

   const options = { day: 'numeric', month: 'long', year: 'numeric' };

   const formatter = new Intl.DateTimeFormat('he-IL-u-ca-hebrew', options);

   ```

   - This creates a date formatter for the Hebrew calendar ('ca-hebrew') in the Israeli locale ('he-IL').

   - It's set to output the day as a number, month as a full name, and year as a number.

2. **Date Formatting:**

   ```javascript

   const parts = formatter.formatToParts(gregorianDate);

   ```

   - This method breaks down the formatted date into its constituent parts (day, month, year).

3. **Custom Formatting:**

   The code then iterates through these parts to create a custom Hebrew date string:

   - For the day: It either uses the numeric value or converts it to Hebrew numerals.

   - For the month: It uses the Hebrew month name provided by the formatter.

   - For the year: It either uses the numeric value or converts it to traditional Hebrew year notation.

4. **Hebrew Numerals Conversion:**

   - Days are converted using a predefined array of Hebrew numerals.

   - Years are converted using a more complex function that handles the thousands, hundreds, tens, and ones places separately.

5. **Underlying Calculation:**

   While the code doesn't explicitly perform the conversion calculations, the `Intl.DateTimeFormat` API is doing this behind the scenes. The conversion involves:

   - Accounting for the different lengths of Hebrew and Gregorian years.

   - Handling the 19-year Metonic cycle in the Hebrew calendar, which aligns the lunar months with the solar year.

   - Adjusting for the Hebrew calendar's leap months.

6. **Key Differences:**

   - The Hebrew calendar is lunisolar, based on moon phases and the solar year.

   - Hebrew days begin at sunset.

   - Hebrew years are counted from the traditional Jewish date of the world's creation.

   - The Hebrew calendar has leap months rather than leap days.

This approach leverages the browser's built-in localization capabilities, ensuring accuracy and reducing the need for complex custom calculations. However, it also means the code is dependent on the browser's implementation of the Hebrew calendar.