Milesian_calendar_conversion.php

<?php 
/*
Conversion from Julian Day to Milesian date and the reverse. 
Written after a version under Ada
Tested under PHP 5.4.x.

The purpose of this package is to provide conversion routines 
between a Julian Day the equivalent date in the Milesian calendar.
Main functions:
	milesiantojd ($month, $day, $year) - similar to gregoriantojd, but arguments represent a date of the Milesian calendar.
	cal_from_jd_milesian ($jd) - similar to cal_from_jd, specifically for the milesian calendar 
		which is not referenced under the PHP user community.
	french_weekday_name ($dow, $title) - yields the complete name of the weekdays in French, beginning or not with a capital.
Other functions are useful for the above mentioned, and are available for broader use: 
	intdiv_a is a special implementation of intdiv (not available under PHP 5.4.x), so that the remainder is non-negative.
	intdiv_r does the same, except that the first argument is by reference, it holds the remainder on return.
	intidiv_r_ceiling is the integer division with positive remainder and ceiling: the remainder may be set to
		the divisor, when the ordinary quotient reaches the ceiling. 
This routine is used e.g. to find the rank of year and of day in the year, in a quadriannum whose last year is the longest.
Caution: all arguments are deemed integers (int). Control cannot be performed before PHP 7.

Version
	2016: Original (translated from Ada)
	2019: 
		Solar intercalation rule is exactly the same as for the Gregorian calendar
		Computations are possible with same limits as other calendars namely: JD <= 536838930, year <= 1465102
		Error handling: like for other calendar, return array 0 0 0
*/
/*
Copyright Miletus 2016-2019 - Louis A. de Fouquières
Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
	1. The above copyright notice and this permission notice shall be included
	in all copies or substantial portions of the Software.
	2. Changes with respect to any former version shall be documented.

The software is provided "as is", without warranty of any kind,
express of implied, including but not limited to the warranties of
merchantability, fitness for a particular purpose and noninfringement.
In no event shall the authors of copyright holders be liable for any
claim, damages or other liability, whether in an action of contract,
tort or otherwise, arising from, out of or in connection with the software
or the use or other dealings in the software.
Inquiries: www.calendriermilesien.org
*/

function intdiv_a ($argument, $divisor) {  //here only values of arguments are passed. 
//Almost the PHP 7.xx intdiv(), except that remainder is always >=0
$cycle = 0;
if ($divisor == 0) throw new DomainException("Divisor cannot be 0");
while ($argument < 0 and $divisor != 0) {
	$argument += $divisor;
	--$cycle;
};
while ($argument >= $divisor and $divisor != 0) {
	$argument -= $divisor;
	++$cycle;
	};
return $cycle;
}
function intdiv_r (&$argument, $divisor) { //same as above, except that first $argument (dividend) is changed to positive remainder
$cycle = 0;
if ($divisor == 0)throw new DomainException("Divisor cannot be 0");
while ($argument < 0) {
	$argument += $divisor;
	--$cycle;
	};
while ($argument >= $divisor) {
	$argument -= $divisor;
	++$cycle;
	};
return $cycle;
}
function intdiv_r_ceil (&$argument, $divisor, $ceiling) { //variant for intdiv_r; $argument is authorised to be = $divisor if it is was originally equal to $ceiling * $divisor
$cycle = 0;
if ($divisor <= 0 or $argument < 0 or $argument > $ceiling * $divisor) throw new DomainException("Invalid arguments for a division with ceiling");
--$ceiling; // in practical, test is performed against $ceiling - 1
while ($argument >= $divisor and $cycle < $ceiling) {
	$argument -= $divisor;
	++$cycle;
	};
return $cycle;
}
function long_milesian_year ($year) { // boolean, says whether $year (milesian) is 366 days long or not.
// $year must be int, this cannot be controlled before PHP 7.x
If ($year < -4713 or $year > 1465102) throw new DomainException("Year is out of range or ill specified");
$year += 4801; // set to a positive number, because modulus computation does not handle properly negative numbers.
return $year % 4 == 0 and ($year % 100 != 0 or $year % 400 == 0) ; 
}
function milesiantojd ($month, $day, $year) { // similar to gregoriantojd; control of validity of milesian date, year between -4713 and +9999.
	if  (($year < -4713) or $year > 1465102) return 0; //throw new DomainException("Year is out of range or ill-specified");
	if	((($month <=0) or ($month > 12)) 
	or (($day <=0) or ($day >31)) 
	or (($day == 31) and ($month % 2 == 1)) 
	or ($month == 12 and $day == 31 and ! long_milesian_year($year)))
	return 0; //throw new DomainException("This date does not exist");
	//Compute from 1 1m 000; this is OK using intdiv_a and not the standard intdiv integer division.
	return max (0,	// If computation leads to 0 or less, return 0; should raise an error.
		(1721049 + $year*365 + intdiv_a($year,4) - intdiv_a($year,100) + intdiv_a($year,400) 
		+ --$month*30 +intdiv_a($month,2)) +$day
		);
}
function cal_from_jd_milesian ($jd){ //an extension of the cal_from_jd routine defined since php 4.1.0., for the Milesian calendar. 
//Names suitable to the Milesian calendar
//The month names are in Latin (although there is a proposed English list for the Milesian months
//The abbreviated names are the universal notation 1m, 2m, 3m etc. through 12m.
//Const 
$MILESIAN_MONTH_LATIN = array ("unemis", "secondemis", "tertemis", 
	"quartemis", "quintemis", "sextemis", 
	"septemis", "octemis", "novemis", 
	"decemis", "undecemis", "duodecemis");
//Const
$MILESIAN_MONTH_NOTATION = array ("1m", "2m", "3m", "4m", "5m", "6m", "7m", "8m", "9m", "10m", "11m", "12m");
//
if ($jd <= 0 or $jd >  536838930) return array ( // throw new DomainException("Julian Day is out of range or ill-specified");
	"date" => "",
	"day" => 0,
	"month" => 0,
	"year" => 0,
	"dow" => 0,
	"abbrevdayname" => "",
	"dayname" => "",
	"abbrevmonth" => "",
	"monthname" => "",	
	);
$day = $jd-1721050; // day counted from 1 1m 0; it may be negative.
// In the next computations, $day is set to the positive remainder of the integer division, 
// whereas the quotient is directly used to compute the year then the month.
$year = 400 * intdiv_r ($day, 146097); 
$year += intdiv_r_ceil ($day, 36524, 4) * 100; 
$year += intdiv_r ($day, 1461) * 4;
$year += intdiv_r_ceil ($day, 365, 4);
$month = intdiv_r ($day, 61) * 2; // initiate rank of month
$month += intdiv_r_ceil ($day, 30, 2); // This is the month rank (from 0). Enough for this purpose.
$day++; //Add one because days are counted starting from 1, not from 0.
return array (
"date" => $day." ".$MILESIAN_MONTH_NOTATION[$month]." ".$year,
"month" => $month+1,
"day" => $day,
"year" => $year,
"dow" => jddayofweek ($jd),
"abbrevdayname" => jddayofweek ($jd, 2),
"dayname" => jddayofweek ($jd, 1),
"abbrevmonth" => $MILESIAN_MONTH_NOTATION [$month],
"monthname" => $MILESIAN_MONTH_LATIN [$month],
);
}
function french_weekday_name ($dow, $title = 0) {
// French names for weekdays
//Const 
$FRENCH_WEEKDAY_NOTITLE = array ("dimanche", "lundi", "mardi", "mercredi", "jeudi", "vendredi", "samedi");
$FRENCH_WEEKDAY_TITLE = array ("Dimanche", "Lundi", "Mardi", "Mercredi", "Jeudi", "Vendredi", "Samedi");
//
	if ($title) {return $FRENCH_WEEKDAY_TITLE[$dow];}
	else {return $FRENCH_WEEKDAY_NOTITLE[$dow];};
}
?>