src/Calendar.php
public function setFirstWeekday($firstWeekday = 0)
	{
		$this->firstWeekday = is_string($firstWeekday)
				? self::firstWeekday($firstWeekday)
				: $firstWeekday;
		$this->buildWeekdays = true;
		return $this;
	}
public function setFirstWeekday($firstWeekday = 0)
	{
		$this->firstWeekday = is_string($firstWeekday)
				? self::firstWeekday($firstWeekday)
				: $firstWeekday;
		$this->buildWeekdays = true;
		return $this;
	}
public function setFirstWeekday ( $ firstWeekday = 0 ) { $ this -> firstWeekday = is_string ( $ firstWeekday ) ? self :: firstWeekday ( $ firstWeekday ) : $ firstWeekday ; $ this -> buildWeekdays = true ; return $ this ; }
Sets the first day of the week in a calendar page view.

@link http://unicode.org/repos/cldr/trunk/common/supplemental/supplementalData.xml

@param  int|string  $firstWeekday  0 (for Monday) through 6 (for Sunday)
or an ISO 3166 country code for example
<code>BR</code> for Brazil, <code>SE</code> for Sweden.
@return Calendar
Sets the first day of the week in a calendar page view .