DateComponents的错误？

Question

我有一个简单的问题：

func findWeekNumber(day: Int, month: Int, year: Int) {
    var calendar = Calendar.current
    var newEventComponents = DateComponents()
    newEventComponents.day = day
    newEventComponents.month = month
    newEventComponents.year = year
    var newEventDate = calendar.date(from: newEventComponents)
    var newEventWeekNumber = calendar.dateComponents([.weekOfYear], from: newEventDate!)
    var weeknumber = newEventWeekNumber.weekOfYear!
    print("The date lies in week: \(weeknumber)")
}

findWeekNumber(day: 30, month: 12, year: 2020)

这会打印1，但应该是53。我在做什么错或者是错误？