在iOS 15中使用如下代码:

extension Date {
    var string: String {
        if #available(iOS 15.0, *) {
            return self.formatted(date: .complete, time: .complete)
        } else {
            return self.description
        }
    }
}

要将2016-02-29 12:24:26转换为日期，使用以下日期格式化程序:

let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd hh:mm:ss"

编辑:获取输出2016年2月29日使用这个日期格式化器:

let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "MMM dd, yyyy"

如果你想解析"1996-12-19T16:39:57-08:00"的日期，请使用以下格式"yyyy-MM-dd 'HH:mm:ssZZZZZ":

let RFC3339DateFormatter = DateFormatter()
RFC3339DateFormatter.locale = Locale(identifier: "en_US_POSIX")
RFC3339DateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZZZZZ"
RFC3339DateFormatter.timeZone = TimeZone(secondsFromGMT: 0)

/* 39 minutes and 57 seconds after the 16th hour of December 19th, 1996 with an offset of -08:00 from UTC (Pacific Standard Time) */
let string = "1996-12-19T16:39:57-08:00"
let date = RFC3339DateFormatter.date(from: string)

来自Apple https://developer.apple.com/documentation/foundation/dateformatter

你必须声明2个不同的NSDateFormatters，第一个将字符串转换为NSDate，第二个以你的格式打印日期。 试试下面的代码:

let dateFormatterGet = NSDateFormatter()
dateFormatterGet.dateFormat = "yyyy-MM-dd HH:mm:ss"

let dateFormatterPrint = NSDateFormatter()
dateFormatterPrint.dateFormat = "MMM dd,yyyy"

let date: NSDate? = dateFormatterGet.dateFromString("2016-02-29 12:24:26")
print(dateFormatterPrint.stringFromDate(date!))

Swift 3级及以上:

从Swift 3 NSDate类已更改为日期和NSDateFormatter到DateFormatter。

let dateFormatterGet = DateFormatter()
dateFormatterGet.dateFormat = "yyyy-MM-dd HH:mm:ss"

let dateFormatterPrint = DateFormatter()
dateFormatterPrint.dateFormat = "MMM dd,yyyy"

if let date = dateFormatterGet.date(from: "2016-02-29 12:24:26") {
    print(dateFormatterPrint.string(from: date))
} else {
   print("There was an error decoding the string")
}

Swift - 5.0

let date = Date()
let format = date.getFormattedDate(format: "yyyy-MM-dd HH:mm:ss") // Set output format

extension Date {
   func getFormattedDate(format: String) -> String {
        let dateformat = DateFormatter()
        dateformat.dateFormat = format
        return dateformat.string(from: self)
    }
}

Swift - 4.0

2018-02-01T19:10:04+00:00

extension Date {
    static func getFormattedDate(string: String , formatter:String) -> String{
        let dateFormatterGet = DateFormatter()
        dateFormatterGet.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZ"
        
        let dateFormatterPrint = DateFormatter()
        dateFormatterPrint.dateFormat = "MMM dd,yyyy"
        
        let date: Date? = dateFormatterGet.date(from: "2018-02-01T19:10:04+00:00")
        print("Date",dateFormatterPrint.string(from: date!)) // Feb 01,2018
        return dateFormatterPrint.string(from: date!);
    }
}

斯威夫特3

let date : Date = Date()
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "MMM dd, yyyy"
let todaysDate = dateFormatter.string(from: date)