How to Converts a Gregorian date to a Julian Day Count in PHP ?

In PHP, we can convert a Gregorian date to a Julian Day Count using the gregoriantojd() function. This function takes three arguments: the month, day, and year of the Gregorian date, and returns the Julian Day Count.

Here's an example:

$jd = gregoriantojd(8, 17, 2021);
echo $jd; // Output: 2459445

In this example, we pass the month (8), day (17), and year (2021) of the Gregorian date to the gregoriantojd() function, which returns the Julian Day Count (2459445).

Alternatively, we can use the DateTime class in PHP to convert a Gregorian date to a Julian Day Count. Here's an example:

$date = new DateTime('2021-08-17');
$jd = $date->format('U') / (60 * 60 * 24) + 2440587.5;
echo $jd; // Output: 2459445.5

In this example, we create a new DateTime object with the Gregorian date '2021-08-17'. We then use the format() method to get the Unix timestamp of the date, which we divide by the number of seconds in a day (60 * 60 * 24) and add to the Julian Day Count of January 1, 4713 BC (2440587.5) to get the Julian Day Count of the Gregorian date (2459445.5).

Note that the gregoriantojd() function returns an integer Julian Day Count, while the DateTime method returns a floating-point Julian Day Count.