<?php
	/* http://andy.bezbozhny.com/webdev/jday/ */

	class jday_class {
		public $year = 0;
		public $month = 0;
		public $day = 0;
		public $jday = 0;

		// Convert Unix timestamp to Julian Day
		// unixtojd
		public function date2jday($unixTimeStamp = 0) {
			if (!$unixTimeStamp) {
				$unixTimeStamp = time();
			}
			$this->dt = $unixTimeStamp;
			$data = getdate($unixTimeStamp);
			$this->year = $data['year'];
			$this->month = $data['mon'];
			$this->day = $data['mday'];
			return $this->gcal2jday($this->month, $this->day, $this->year);
		}

		// Converts a Gregorian Calendar date to Julian Day
		// GregorianToJD
		public function gcal2jday($month, $day, $year) {
			if (checkdate($month, $day, $year)) {
				$a = floor((14 - $month) / 12);
				$y = floor($year + 4800 - $a);
				$m = floor($month + 12 * $a - 3);
				return $this->jday = $day + floor((153 * $m + 2) / 5) + $y * 365 + floor($y / 4) - floor($y / 100) + floor($y / 400) - 32045;
			} else {
				return false;
			}
		}

		// Convert Julian Day to Unix timestamp
		// jdtounix
		public function jday2date($jd) {
			$l = $jd + 68569;
			$n = $this->aint((4 * $l) / 146097);
			$l = $l - $this->aint((146097 * $n + 3) / 4);
			$i = $this->aint((4000 * ($l + 1)) / 1461001);
			$l = $l - $this->aint((1461 * $i) / 4) + 31;
			$j = $this->aint((80 * $l) / 2447);
			$this->day = $l - $this->aint((2447 * $j) / 80);
			$l = $this->aint($j / 11);
			$this->month = $j + 2 - (12 * $l);
			$this->year = 100 * ($n - 49) + $i + $l;
			return mktime(0, 0, 0, $this->month, $this->day, $this->year);
		}

		private function aint($value) {
			if ($value > 0) {
				return floor($value);
			} else {
				return ceil($value);
			}
		}
	}
?>