Swift：日期字符串只有月份和年份，我还可以生成日期吗？(Swift: Date string only has month and year, can I still produce a date?)

 我正在将一些旧的Javascript代码移植到Swift应用程序，我的客户端的数据集有点奇怪，因为它们只记录了每个日期的月份和年份，所以安装日期字符串看起来像： 2001-05 。 
 
 在Javascript中我可以使用： var date = new Date("2001-05"); 它返回的内容： 2001-05-01T00:00:00.000Z将时间/日归零，但按预期保持年和月。 
 
 我目前在Swift中使用以下代码： 
 
var date = "2001-05"

func stringToDate(_ date: String) -> Date? {
    let df = DateFormatter()
    df.locale = NSLocale(localeIdentifier: "en_US_POSIX") as Locale!
    df.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZZZZ"

    return df.date(from: date)
}

print(stringToDate(date))
 
 这总是产生零输出。 是否有可能在Swift中重现日期格式的JS行为？ 

I'm porting some old Javascript code to a Swift app, my data-set from my client is a little strange in that they recorded just the month and year of each date, so an installation date string would look like: 2001-05.
 
In Javascript I can use: var date = new Date("2001-05"); to which it returns: 2001-05-01T00:00:00.000Z zeroing the time/day but maintaining the year and month as expected.
 
I currently use the below code in Swift:
 
var date = "2001-05"

func stringToDate(_ date: String) -> Date? {
    let df = DateFormatter()
    df.locale = NSLocale(localeIdentifier: "en_US_POSIX") as Locale!
    df.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZZZZ"

    return df.date(from: date)
}

print(stringToDate(date))
 
This always produces a nil output. Is it possible to reproduce the JS behaviour of date-formatting in Swift?

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