Swift版本:5.6 +以上

DateFormatter的DateFormatter属性用于用自定义字符串模式格式化日期。

let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "MMM dd, yyyy"
    
let date = dateFormatter.string(from: datePicker.date)
print(date)
//Feb 28, 2022

如果你想要任何不应该格式化和打印的东西，那么在这个单词周围使用单引号。像;“在”

dateFormatter.dateFormat = "MMM dd, yyyy 'at' hh:MM a"
// May 29, 2022 at 12:05 PM

这些都是格式化日期、时间和时区的可能模式。

Swift 3与日期扩展

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

然后你可以这样使用它:

let date = Date()
date.string(with: "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

Swift 3及以上

let dateFormatter = DateFormatter()
dateFormatter.dateStyle = .medium
dateFormatter.timeStyle = .none
dateFormatter.locale = Locale.current
print(dateFormatter.string(from: date)) // Jan 2, 2001

当你想本地化你的应用程序时，这也是有帮助的。Locale(identifier:)使用ISO 639-1代码。 请参见Apple文档

将@BatyrCan转换为Swift 5.3的额外格式。在Xcode 12中测试。

let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "HH:mm:ss"
var dateFromStr = dateFormatter.date(from: "12:16:45")!

dateFormatter.dateFormat = "hh:mm:ss a 'on' MMMM dd, yyyy"
//Output: 12:16:45 PM on January 01, 2000

dateFormatter.dateFormat = "E, d MMM yyyy HH:mm:ss Z"
//Output: Sat, 1 Jan 2000 12:16:45 +0600

dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZ"
//Output: 2000-01-01T12:16:45+0600

dateFormatter.dateFormat = "EEEE, MMM d, yyyy"
//Output: Saturday, Jan 1, 2000

dateFormatter.dateFormat = "MM-dd-yyyy HH:mm"
//Output: 01-01-2000 12:16

dateFormatter.dateFormat = "MMM d, h:mm a"
//Output: Jan 1, 12:16 PM

dateFormatter.dateFormat = "HH:mm:ss.SSS"
//Output: 12:16:45.000

dateFormatter.dateFormat = "MMM d, yyyy"
//Output: Jan 1, 2000

dateFormatter.dateFormat = "MM/dd/yyyy"
//Output: 01/01/2000

dateFormatter.dateFormat = "hh:mm:ss a"
//Output: 12:16:45 PM

dateFormatter.dateFormat = "MMMM yyyy"
//Output: January 2000

dateFormatter.dateFormat = "dd.MM.yy"
//Output: 01.01.00

//Customisable AP/PM symbols
dateFormatter.amSymbol = "am"
dateFormatter.pmSymbol = "Pm"
dateFormatter.dateFormat = "a"
//Output: Pm

// Usage
var timeFromDate = dateFormatter.string(from: dateFromStr)
print(timeFromDate)

斯威夫特3

func dataFormat(dataJ: Double) -> String {

        let dateFormatter = DateFormatter()
        dateFormatter.dateStyle = .long
        dateFormatter.timeStyle = .none
        let date = Date(timeIntervalSince1970: dataJ)
        return (dataJ != nil) ? "Today, \(dateFormatter.string(from: date))" : "Date Invalid"

    }