calendar-bundle/src/Resources/contao/classes/Calendar.php
public static function unixToJd($tstamp)
	{
		list($year, $month, $day) = explode(',', date('Y,m,d', $tstamp));

		// Make year a positive number
		$year += ($year < 0 ? 4801 : 4800);

		// Adjust the start of the year
		if ($month > 2)
		{
			$month -= 3;
		}
		else
		{
			$month += 9;
			--$year;
		}

		$sdn  = floor((floor($year / 100) * 146097) / 4);
		$sdn += floor((($year % 100) * 1461) / 4);
		$sdn += floor(($month * 153 + 2) / 5);
		$sdn += $day - 32045;

		return $sdn;
	}
public static function unixToJd($tstamp)
	{
		list($year, $month, $day) = explode(',', date('Y,m,d', $tstamp));

		// Make year a positive number
		$year += ($year < 0 ? 4801 : 4800);

		// Adjust the start of the year
		if ($month > 2)
		{
			$month -= 3;
		}
		else
		{
			$month += 9;
			--$year;
		}

		$sdn  = floor((floor($year / 100) * 146097) / 4);
		$sdn += floor((($year % 100) * 1461) / 4);
		$sdn += floor(($month * 153 + 2) / 5);
		$sdn += $day - 32045;

		return $sdn;
	}
Convert a UNIX timestamp to a Julian day

@param integer $tstamp

@return integer