gregoriantojd

(PHP 4, PHP 5, PHP 7, PHP 8)

gregoriantojd — Converts a Gregorian date to Julian Day Count

Опис

gregoriantojd(int $month, int $day, int $year): int

The valid range for the Gregorian calendar is from November 25, 4714 B.C. to at least December 31, 9999 A.D.

Although this function can handle dates all the way back to 4714 B.C., such use may not be meaningful. The Gregorian calendar was not instituted until October 15, 1582 (or October 5, 1582 in the Julian calendar). Some countries did not accept it until much later. For example, Britain converted in 1752, The USSR in 1918 and Greece in 1923. Most European countries used the Julian calendar prior to the Gregorian.

Параметри

month: The month as a number from 1 (for January) to 12 (for December)
day: The day as a number from 1 to 31. If the month has less days then given, overflow occurs; see the example below.
year: The year as a number between -4714 and 9999. Negative numbers mean years B.C., positive numbers mean years A.D. Note that there is no year 0; December 31, 1 B.C. is immediately followed by January 1, 1 A.D.

Значення, що повертаються

The julian day for the given gregorian date as an integer. Dates outside the valid range return 0.

Приклади

Приклад #1 Calendar functions

<?php
$jd = gregoriantojd(10, 11, 1970);
echo "$jd\n";
$gregorian = jdtogregorian($jd);
echo "$gregorian\n";
?>

Поданий вище приклад виведе:

2440871
10/11/1970

Приклад #2 Overflow behavior

<?php
echo gregoriantojd(2, 31, 2018), PHP_EOL,
     gregoriantojd(3,  3, 2018), PHP_EOL;
?>

Поданий вище приклад виведе:

2458181
2458181

Прогляньте також

jdtogregorian() - Converts Julian Day Count to Gregorian date
cal_to_jd() - Converts from a supported calendar to Julian Day Count

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User Contributed Notes 3 notes

down

jettyrat at jettyfishing dot com ¶

19 years ago

You can obtain the decimal fraction of the Julian date with the php gregoriantojd() function or the function shown below by applying this code to the returned value.



<?php

  $julianDate = gregoriantojd($month, $day, $year);



  //correct for half-day offset

  $dayfrac = date('G') / 24 - .5;

  if ($dayfrac < 0) $dayfrac += 1;



  //now set the fraction of a day

  $frac = $dayfrac + (date('i') + date('s') / 60) / 60 / 24;



  $julianDate = $julianDate + $frac;

?>

down

httpwebwitch ¶

20 years ago

This function also ignores decimal fractions in JD dates, and it uses non-standard format for returning the Gregorian date. 

So, if your JD date is 2453056.28673, the Gregorian returned value is 2/20/2004, not "2004-02-20 23:45:36"

The decimal part is important, since the Julian day begins at noon, for example 2453056.49 is on Friday, 2453056.50 is on Saturday. Discarding the decimal part means that your returned Gregorian Date will be wrong 50% of the time.

down

-1

jfg ¶

15 years ago

If you need the same output as the g_date_get_julian function of the GlibC, here is my php implementation :

<?php
    /**
     * Glib g_date_get_julian PHP implementation
     *
     * @param  $str  Date string in a format accepted by strtotime
     * @author jfg
     */
    private function _get_julian( $str )
    {
        $d = date_create($str);

        if( $d == false )
            return 0;
        
        $day_in_year = (int) date_format($d, "z");
        $year        = (int) date_format($d, "Y") - 1;
        $julian_days = $year * 365;
        $julian_days += ($year >>= 2);
        $julian_days -= ($year /= 25);
        $julian_days += $year >> 2;
        $julian_days += $day_in_year + 1;

        return ceil($julian_days);
    }

?>

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