cal_from_jd: Converting Julian date count to any other calendar

$jdday_number = cal_to_jd(CAL_JULIAN,12,4,2013);
print_r(cal_from_jd($jdday_number,CAL_JULIAN));

The output is here

Array ( [date] => 12/4/2013 [month] => 12 [day] => 4 [year] => 2013 [dow] => 2 [abbrevdayname] => Tue [dayname] => Tuesday [abbrevmonth] => Dec [monthname] => December )

Julian Day Numbers (JDN) are a continuous count of days starting from January 1, 4713 BCE (proleptic Julian calendar). They are primarily used in astronomy and scientific calculations to avoid complications related to leap years, time zones, and calendar changes. Each day is assigned a unique number, which simplifies the calculation of the number of days between two dates across different calendar systems. The Julian Day Number starts at noon UTC, making it especially useful for precise timekeeping.

For example, January 1, 2000 in the Gregorian calendar corresponds to JDN 2451545.

By using Julian day count ( Integer value ) we can get the calendar details like month , day , day of the week, year etc ( in the form of an array ). Syntax is here.

cal_from_jd(julian_day INT,CAL_GREGORIAN)

Example 1: Converting Julian Day to Gregorian Date

This example demonstrates how to convert a Julian Day Number to a Gregorian calendar date using cal_from_jd().

$jd = 2451545;  // Example Julian Day
$date = cal_from_jd($jd, CAL_GREGORIAN);
print_r($date);

Output:

Array
(
    [date] => 1/1/2000
    [month] => 1
    [day] => 1
    [year] => 2000
    [dow] => 6
    [abbrevdayname] => Sat
    [dayname] => Saturday
    [abbrevmonth] => Jan
    [monthname] => January
)
1

---

Example 2: Converting Julian Day to Jewish Calendar Date

This example converts a Julian Day Number to the Jewish calendar system using cal_from_jd().

$jd = 2451545;  // Example Julian Day
$date = cal_from_jd($jd, CAL_JEWISH);
print_r($date);

Output:

Array
(
    [date] => 4/23/5760
    [month] => 4
    [day] => 23
    [year] => 5760
    [dow] => 6
    [abbrevdayname] => Sat
    [dayname] => Saturday
    [abbrevmonth] => Tevet
    [monthname] => Tevet
)

---

Example 3: Converting Julian Day to French Republican Calendar

This example demonstrates converting a Julian Day Number into the French Republican calendar system.

$jd = 2375840;  // Example Julian Day
$date = cal_from_jd($jd, CAL_FRENCH);
print_r($date);

Output:

Array
(
    [date] => 1/1/1
    [month] => 1
    [day] => 1
    [year] => 1
    [dow] => 6
    [abbrevdayname] => Sat
    [dayname] => Saturday
    [abbrevmonth] => Vendemiaire
    [monthname] => Vendemiaire
)

Demo of how Unix timestamp is used to generate Julian Day and Calendar
Calendar Functions

Subhendu Mohapatra

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cal_from_jd: getting Calendar from Julian day Number

Example 1: Converting Julian Day to Gregorian Date

Example 2: Converting Julian Day to Jewish Calendar Date

Example 3: Converting Julian Day to French Republican Calendar

Subhendu Mohapatra