# Frenchtojd()

## Introduction

Before we dive into the nitty-gritty details of French-to-Julian day conversion in PHP, let's start with a brief introduction. Julian day is the continuous count of days since the beginning of the Julian period, which began on January 1, 4713 BC. It is widely used in astronomy, physics, and other fields where continuous time measurement is required.

French Republican Calendar, on the other hand, was a calendar used in France from 1793 to 1805. It was designed to replace the Gregorian calendar, and it was based on the principles of the French Revolution. The calendar was divided into 12 months, each with three ten-day weeks.

Converting French dates to Julian days in PHP requires some complex calculations, but with the right approach and knowledge, you can easily do it.

## The PHP Function for French-to-Julian Day Conversion

To convert a French date to a Julian day in PHP, we can use the following function:

``````<?php

function frenchtojd(\$month, \$day, \$year) {
\$a = floor((14 - \$month) / 12);
\$y = \$year + 4800 - \$a;
\$m = \$month + 12 * \$a - 3;
\$jd = \$day + floor((153 * \$m + 2) / 5) + 365 * \$y + floor(\$y / 4) - floor(\$y / 100) + floor(\$y / 400) - 32045;
return \$jd;
}``````

Let's break down this function to understand how it works.

The first step is to calculate the year, month, and day from the French date. We subtract 14 from the month and divide the result by 12, rounding down to get the variable \$a. Then, we calculate \$y by adding 4800 to the year and subtracting \$a. Next, we calculate \$m by adding 12 times \$a to the month and subtracting 3. Finally, we use the formula to calculate the Julian day (\$jd) based on the values of \$day, \$m, \$y, and other constants.

## Example Usage

To use this function, simply pass in the month, day, and year of the French date as parameters. For example:

``````<?php

\$jd = frenchtojd(8, 22, 1793);
echo \$jd; // Output: 2378491``````

In this example, we're converting the French date "22 Fructidor, Year I" to a Julian day.

## Conclusion

In conclusion, converting French dates to Julian days in PHP requires some complex calculations, but with the right approach and knowledge, you can easily do it. We hope this article has provided you with everything you need to know to successfully convert French dates to Julian days using PHP. If you have any questions or comments, feel free to leave them below.