Hebrew Date Calculation Algorithm

Web deployment: Hebrew Date Calculator Chrome Extension: Hebrew Date Calculator 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:

   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:

   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.