// Which week numbering year is 26 December 2004 with the default settings?
var result = getWeekYear(new Date(2004, 11, 26))
//=> 2005
// Which week numbering year is 26 December 2004 if week starts on Saturday?
var result = getWeekYear(new Date(2004, 11, 26), { weekStartsOn: 6 })
//=> 2004
// Which week numbering year is 26 December 2004 if the first week contains 4 January?
var result = getWeekYear(new Date(2004, 11, 26), { firstWeekContainsDate: 4 })
//=> 2004