我建议默认添加时区。我将展示一个swift 5的例子 1. 新增扩展文件Date+Formatter.swift

import Foundation

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

使用的例子

    let date = Date()
    let dateString = date.getFormattedDateString(format: "yyyy-MM-dd HH:mm:ss")
    print("dateString > \(dateString)")
    // print
    // dateString > 2020-04-30 15:15:21

我解决了我的问题格式yyyy-MM-dd' t ' hh:mm:ss.SSS' z '(e。g 2018-06-15T00:00:00.000Z)

func formatDate(date: String) -> String {
   let dateFormatterGet = DateFormatter()
   dateFormatterGet.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"

   let dateFormatter = DateFormatter()
   dateFormatter.dateStyle = .medium
   dateFormatter.timeStyle = .none
   //    dateFormatter.locale = Locale(identifier: "en_US") //uncomment if you don't want to get the system default format.

   let dateObj: Date? = dateFormatterGet.date(from: date)

   return dateFormatter.string(from: dateObj!)
}

只需使用以下函数转换日期格式:-

  let convertedFormat =  convertToString(dateString: "2019-02-12 11:23:12", formatIn: "yyyy-MM-dd hh:mm:ss", formatOut: "MMM dd, yyyy")    //calling function

   print(convertedFormat) // feb 12 2019


 func convertToString (dateString: String, formatIn : String, formatOut : String) -> String {

    let dateFormater = DateFormatter()
    dateFormater.timeZone = NSTimeZone(abbreviation: "UTC") as TimeZone!
    dateFormater.dateFormat = formatIn
    let date = dateFormater.date(from: dateString)

    dateFormater.timeZone = NSTimeZone.system

    dateFormater.dateFormat = formatOut
    let timeStr = dateFormater.string(from: date!)
    return timeStr
 }

Swift 3版本用新的Date对象代替NSDate:

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

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

let date: Date? = dateFormatterGet.date(from: "2017-02-14 17:24:26")
print(dateFormatter.string(from: date!))

编辑:在mitul-nakum建议之后

格式日期的另一个有趣的可能性。此截图属于苹果App“News”。

代码如下:

let dateFormat1 = DateFormatter()
dateFormat1.dateFormat = "EEEE"
let stringDay = dateFormat1.string(from: Date())

let dateFormat2 = DateFormatter()
dateFormat2.dateFormat = "MMMM"
let stringMonth = dateFormat2.string(from: Date())

let dateFormat3 = DateFormatter()
dateFormat3.dateFormat = "dd"
let numDay = dateFormat3.string(from: Date())

let stringDate = String(format: "%@\n%@ %@", stringDay.uppercased(), stringMonth.uppercased(), numDay)

对于lorenzoliveto提出的替代方案，没什么可补充的。太完美了。

let dateFormat = DateFormatter()
dateFormat.dateFormat = "EEEE\nMMMM dd"
let stringDate = dateFormat.string(from: Date()).uppercased()

    import UIKit
    // Example iso date time
    let isoDateArray = [
        "2020-03-18T07:32:39.88Z",
        "2020-03-18T07:32:39Z",
        "2020-03-18T07:32:39.8Z",
        "2020-03-18T07:32:39.88Z",
        "2020-03-18T07:32:39.8834Z"
    ]


    let dateFormatterGetWithMs = DateFormatter()
    let dateFormatterGetNoMs = DateFormatter()

// Formater with and without millisecond 
    dateFormatterGetWithMs.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"
    dateFormatterGetNoMs.dateFormat = "yyyy-MM-dd'T'HH:mm:ss'Z'"

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

    for dateString in isoDateArray {
        var date: Date? = dateFormatterGetWithMs.date(from: dateString)
        if (date == nil){
            date = dateFormatterGetNoMs.date(from: dateString)
        }
        print("===========>",date!)
    }