<?php
// Program: µDate function
// Author: Roger Hågensen (c) µDate 6816.030 - 15:21:23 - Wednesday 1 February 6816
// Version: 1.3
// Purpose: µDate function
// License: BSD

/*
Copyright (c) EmSai, Roger Hågensen 2006
All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* Neither the name of EmSai nor the names of its contributors may be used to endorse
* or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

function jd_to_unidate($jdn)
{
 $jdc=$jdn-0.5; //adjust JDN by 0.5 to get JDC (which Unidate is based around)
 $sign='';
 if ($jdc<0) $sign='-'; //keep track of sign to help us handle negative JDN's.
 $days=abs($jdc);
 if ($days<360) //simplify math if less than a year
 {
  $uniyear=0;
  $uniday=(int)$days;
 }
 else
 {
  $uniyear=(int)($days/360);
  $uniday=(int)($days-($uniyear*360));
 }
 if ($sign)
 {
  $uniday=359-$uniday;
  return '-'.$uniyear.'.'.str_pad($uniday,3,'0',STR_PAD_LEFT);
 }
 else
 {
  return $uniyear.'.'.str_pad($uniday,3,'0',STR_PAD_LEFT);
 }
}

function unidate_to_jd($unidate)
{
 $result=explode('.',$unidate,3);
 $uniyear=0;
 $uniday=0;
 if (count($result)>0)
 {
  $uniyear=$result[0];
  if (count($result)>1)
  {
   $uniday=$result[1];
  }
 }
 if ($uniday<0) $uniday=0; //enforce validity
 if ($uniday>359) $uniday=359; //enforce validity
 if ($uniyear==0 and $uniday==0)
 {
  return 0.5;
 }
 elseif (($uniyear==='-0') or ($uniyear<0))
 {
  return -(float)((abs($uniyear)*360)+(360-$uniday)-0.5);
 }
 else
 {
  return (float)($uniyear*360)+$uniday+0.5;
 }
}

function gregorian_to_unidate($month,$day,$year)
{
 return jd_to_unidate(gregoriantojd($month,$day,$year)-0.5); //PHP's functions really simplify this one thankfully!
}

function unidate_to_gregorian($unidate)
{
 return jdtogregorian(unidate_to_jd($unidate)+0.5); //again PHP's functions really simplify this one!
}

function unidate()
{
 //returns time() in seconds since the unix epoch that starts at midnight 1.1.1970,
 //2440587.5 (1.1.1970) is the JDN of that date which we need to add to get the total JDN since 0,
 //we do this since there exist no native JDN, and PHP unixtojd() returns a rounded integer which is not satisfactory.
 //The result is similar to those by http://aa.usno.navy.mil/data/docs/JulianDate.html
 $jdn=2440587.5+(time()/86400);
 return jd_to_unidate($jdn);
}

function unidate_full()
{
// **** The following is just to give month/day, week/weekday in µDate
// **** to make the concept of µDate not that alien to current systems
// **** and the fact that people like to use months/weeks etc.
// **** µYear.Day is the only true µDate time storage format.

//incomplete example, only handles positive years for now.

//weekday names
$dayname[0]='Sunday';
$dayname[1]='Monday';
$dayname[2]='Tuesday';
$dayname[3]='Wednesday';
$dayname[4]='Thursday';
$dayname[5]='Friday';
$dayname[6]='Saturday';

//month names
$monthname[0]='January';
$monthname[1]='February';
$monthname[2]='Mars';
$monthname[3]='April';
$monthname[4]='May';
$monthname[5]='June';
$monthname[6]='july';
$monthname[7]='August';
$monthname[8]='September';
$monthname[9]='October';
$monthname[10]='November';
$monthname[11]='December';

$unidate=unidate();
$jd=unidate_to_jd($unidate);

list($uyear,$udays)=explode('.',$unidate);

$uweekday=(int)fmod($jd,7);
$umonth=(int)floor($udays/30);
$uday=($udays-($umonth*30))+1;

return '&micro;'.$unidate.' '.gmdate('H:i:s').' ('.$dayname[$uweekday].', '.$monthname[$umonth].' '.$uday.', Year '.$uyear.')';
}
?>