我在Leo Dabus的asnwer中添加了一个“长”版本，以防你想要一个字符串，说“2周前”而不是“2w”……

extension Date {
    func offsetLong(from date: Date) -> String {
        if years(from: date) > 0 {
            return years(from: date) > 1 ? "\(years(from: date)) years ago" : "\(years(from: date)) year ago"
        }
        if months(from: date) > 0 {
            return months(from: date) > 1 ? "\(months(from: date)) months ago" : "\(months(from: date)) month ago" 
        }
        if weeks(from: date) > 0 {
            return weeks(from: date) > 1 ? "\(weeks(from: date)) weeks ago" : "\(weeks(from: date)) week ago"
        }
        if days(from: date) > 0 {
            return days(from: date) > 1 ? "\(days(from: date)) days ago" : "\(days(from: date)) day ago" 
        }
        if hours(from: date) > 0 {
            return hours(from: date) > 1 ? "\(hours(from: date)) hours ago" : "\(hours(from: date)) hour ago"
        }
        if minutes(from: date) > 0 {
            return minutes(from: date) > 1 ? "\(minutes(from: date)) minutes ago" : "\(minutes(from: date)) minute ago"
        }
        if seconds(from: date) > 0 {
            return seconds(from: date) > 1 ? "\(seconds(from: date)) seconds ago" : "\(seconds(from: date)) second ago"
        }
        return ""
    }
}

对于XCode版本8.3.3和Swift 3.0:

    let dateFormatter = DateFormatter()
    dateFormatter.dateStyle = .medium
    dateFormatter.timeStyle = .short

    var beginDate = "2017-08-24 12:00:00"
    var endDate = "2017-09-07 12:00:00"


    let startDateTime = dateFormatter.date(from: beginDate) //according to date format your date string
    print(startDateTime ?? "") //Convert String to Date

    let endDateTime = dateFormatter.date(from: endDate) //according to date format your date string
    print(endDateTime ?? "") //Convert String to Date

    let dateComponentsFormatter = DateComponentsFormatter()
    dateComponentsFormatter.allowedUnits = [NSCalendar.Unit.minute,NSCalendar.Unit.hour,NSCalendar.Unit.day]


   let interval = endDateTime!.timeIntervalSince(startDateTime!)
   var diff = dateComponentsFormatter.string(from: interval)!

   print(diff)

   var day_i  = 0
   var hour_i = 0
   var min_i = 0


     if (diff.contains("d"))
       {
              let day = diff.substring(to: (diff.range(of: "d")?.lowerBound)!)

               day_i  = Int(day)!
               print ("day --> \(day_i)")

               diff = diff.substring(from:(diff.range(of : " ")?.upperBound )!)
               print(diff)
       }


       let hour = diff.substring(to: (diff.range(of : ":")?.lowerBound )!)
       hour_i  = Int(hour)!
       print ("hour --> \(hour_i)")

       let min = diff.substring(from: (diff.range(of : ":")?.upperBound )!)
       min_i  = Int(min)!
       print ("min --> \(min_i)")

你问:

我想有一个函数，比较两个日期，如果(秒> 60)，那么它返回分钟，如果(分钟> 60)返回小时，如果(小时> 24)返回天，等等。

我假设您正在尝试构建两个日期之间经过时间的字符串表示。而不是自己写代码来做这件事，苹果已经有了一个专门设计来做这件事的类。也就是说，使用DateComponentsFormatter，将allowedUnits设置为对你的应用有意义的任何值，将unitsStyle设置为你想要的任何值(例如.full)，然后调用string(from:to:)。

例如，在Swift 3中:

let previousDate = ...
let now = Date()

let formatter = DateComponentsFormatter()
formatter.unitsStyle = .full
formatter.allowedUnits = [.month, .day, .hour, .minute, .second]
formatter.maximumUnitCount = 2   // often, you don't care about seconds if the elapsed time is in months, so you'll set max unit to whatever is appropriate in your case

let string = formatter.string(from: previousDate, to: now)

这也将本地化对应于相关设备的字符串。

或者，在Swift 2.3中:

let previousDate = ...
let now = NSDate()

let formatter = NSDateComponentsFormatter()
formatter.unitsStyle = .Full
formatter.allowedUnits = [.Month, .Day, .Hour, .Minute, .Second]
formatter.maximumUnitCount = 2

let string = formatter.stringFromDate(previousDate, toDate: now)

如果您正在寻找实际的数值，只需使用dateComponents。例如，在Swift 3中:

let components = Calendar.current.dateComponents([.month, .day, .hour, .minute, .second], from: previousDate, to: now)

或者，在Swift 2.3中:

let components = NSCalendar.currentCalendar().components([.Month, .Day, .Hour, .Minute, .Second], fromDate: previousDate, toDate: now, options: [])

Xcode 8.3•Swift 3.1或更高版本

您可以使用日历来帮助您创建一个扩展来进行日期计算，如下所示:

extension Date {
    /// Returns the amount of years from another date
    func years(from date: Date) -> Int {
        return Calendar.current.dateComponents([.year], from: date, to: self).year ?? 0
    }
    /// Returns the amount of months from another date
    func months(from date: Date) -> Int {
        return Calendar.current.dateComponents([.month], from: date, to: self).month ?? 0
    }
    /// Returns the amount of weeks from another date
    func weeks(from date: Date) -> Int {
        return Calendar.current.dateComponents([.weekOfMonth], from: date, to: self).weekOfMonth ?? 0
    }
    /// Returns the amount of days from another date
    func days(from date: Date) -> Int {
        return Calendar.current.dateComponents([.day], from: date, to: self).day ?? 0
    }
    /// Returns the amount of hours from another date
    func hours(from date: Date) -> Int {
        return Calendar.current.dateComponents([.hour], from: date, to: self).hour ?? 0
    }
    /// Returns the amount of minutes from another date
    func minutes(from date: Date) -> Int {
        return Calendar.current.dateComponents([.minute], from: date, to: self).minute ?? 0
    }
    /// Returns the amount of seconds from another date
    func seconds(from date: Date) -> Int {
        return Calendar.current.dateComponents([.second], from: date, to: self).second ?? 0
    }
    /// Returns the a custom time interval description from another date
    func offset(from date: Date) -> String {
        if years(from: date)   > 0 { return "\(years(from: date))y"   }
        if months(from: date)  > 0 { return "\(months(from: date))M"  }
        if weeks(from: date)   > 0 { return "\(weeks(from: date))w"   }
        if days(from: date)    > 0 { return "\(days(from: date))d"    }
        if hours(from: date)   > 0 { return "\(hours(from: date))h"   }
        if minutes(from: date) > 0 { return "\(minutes(from: date))m" }
        if seconds(from: date) > 0 { return "\(seconds(from: date))s" }
        return ""
    }
}

使用日期组件格式化程序

let dateComponentsFormatter = DateComponentsFormatter()
dateComponentsFormatter.allowedUnits = [.second, .minute, .hour, .day, .weekOfMonth, .month, .year]
dateComponentsFormatter.maximumUnitCount = 1
dateComponentsFormatter.unitsStyle = .full
dateComponentsFormatter.string(from: Date(), to: Date(timeIntervalSinceNow: 4000000))  // "1 month"

let date1 = DateComponents(calendar: .current, year: 2014, month: 11, day: 28, hour: 5, minute: 9).date!
let date2 = DateComponents(calendar: .current, year: 2015, month: 8, day: 28, hour: 5, minute: 9).date!

let years = date2.years(from: date1)     // 0
let months = date2.months(from: date1)   // 9
let weeks = date2.weeks(from: date1)     // 39
let days = date2.days(from: date1)       // 273
let hours = date2.hours(from: date1)     // 6,553
let minutes = date2.minutes(from: date1) // 393,180
let seconds = date2.seconds(from: date1) // 23,590,800

let timeOffset = date2.offset(from: date1) // "9M"

let date3 = DateComponents(calendar: .current, year: 2014, month: 11, day: 28, hour: 5, minute: 9).date!
let date4 = DateComponents(calendar: .current, year: 2015, month: 11, day: 28, hour: 5, minute: 9).date!

let timeOffset2 = date4.offset(from: date3) // "1y"

let date5 = DateComponents(calendar: .current, year: 2017, month: 4, day: 28).date!
let now = Date()
let timeOffset3 = now.offset(from: date5) // "1w"

在jose920405中添加了一些答案，使其与Swift 3.0及以上版本兼容

func getDateTimeDiff(dateStr:String) -> String {
    
    let formatter : DateFormatter = DateFormatter()
    formatter.timeZone = NSTimeZone.local
    formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
    
    let now = formatter.string(from: NSDate() as Date)
    let startDate = formatter.date(from: dateStr)
    let endDate = formatter.date(from: now)
    
    // *** create calendar object ***
    var calendar = NSCalendar.current
    
    // *** Get components using current Local & Timezone ***
    print(calendar.dateComponents([.year, .month, .day, .hour, .minute, .second], from: startDate!))
    
    // *** define calendar components to use as well Timezone to UTC ***
    let unitFlags = Set<Calendar.Component>([.year, .month, .day, .hour, .minute, .second])
    calendar.timeZone = TimeZone(identifier: "UTC")!
    let dateComponents = calendar.dateComponents(unitFlags, from: startDate!, to: endDate!)
    
    // *** Get Individual components from date ***
    let years = dateComponents.year!
    let months = dateComponents.month!
    let days = dateComponents.day!
    let hours = dateComponents.hour!
    let minutes = dateComponents.minute!
    let seconds = dateComponents.second!
    
    var timeAgo = ""
    
    if (seconds > 0){
        if seconds < 2 {
            timeAgo = "Second Ago"
        }
        else{
            timeAgo = "\(seconds) Second Ago"
        }
    }
    
    if (minutes > 0){
        if minutes < 2 {
            timeAgo = "Minute Ago"
        }
        else{
            timeAgo = "\(minutes) Minutes Ago"
        }
    }
    
    if(hours > 0){
        if hours < 2 {
            timeAgo = "Hour Ago"
        }
        else{
            timeAgo = "\(hours) Hours Ago"
        }
    }
    
    if (days > 0) {
        if days < 2 {
            timeAgo = "Day Ago"
        }
        else{
            timeAgo = "\(days) Days Ago"
        }
    }
    
    if(months > 0){
        if months < 2 {
            timeAgo = "Month Ago"
        }
        else{
            timeAgo = "\(months) Months Ago"
        }
    }
    
    if(years > 0){
        if years < 2 {
            timeAgo = "Year Ago"
        }
        else{
            timeAgo = "\(years) Years Ago"
        }
    }
    
    DLog("timeAgo is ===> \(timeAgo)")
    return timeAgo;
}

——>使用这个找到时间差距在两个日期在Swift(与两个字符串)。

func timeGapBetweenDates(previousDate : String,currentDate : String)
{
    let dateString1 = previousDate
    let dateString2 = currentDate

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


    let date1 = Dateformatter.date(from: dateString1)
    let date2 = Dateformatter.date(from: dateString2)


    let distanceBetweenDates: TimeInterval? = date2?.timeIntervalSince(date1!)
    let secondsInAnHour: Double = 3600
    let minsInAnHour: Double = 60
    let secondsInDays: Double = 86400
    let secondsInWeek: Double = 604800
    let secondsInMonths : Double = 2592000
    let secondsInYears : Double = 31104000

    let minBetweenDates = Int((distanceBetweenDates! / minsInAnHour))
    let hoursBetweenDates = Int((distanceBetweenDates! / secondsInAnHour))
    let daysBetweenDates = Int((distanceBetweenDates! / secondsInDays))
    let weekBetweenDates = Int((distanceBetweenDates! / secondsInWeek))
    let monthsbetweenDates = Int((distanceBetweenDates! / secondsInMonths))
    let yearbetweenDates = Int((distanceBetweenDates! / secondsInYears))
    let secbetweenDates = Int(distanceBetweenDates!)




    if yearbetweenDates > 0
    {
        print(yearbetweenDates,"years")//0 years
    }
    else if monthsbetweenDates > 0
    {
        print(monthsbetweenDates,"months")//0 months
    }
    else if weekBetweenDates > 0
    {
        print(weekBetweenDates,"weeks")//0 weeks
    }
    else if daysBetweenDates > 0
    {
        print(daysBetweenDates,"days")//5 days
    }
    else if hoursBetweenDates > 0
    {
        print(hoursBetweenDates,"hours")//120 hours
    }
    else if minBetweenDates > 0
    {
        print(minBetweenDates,"minutes")//7200 minutes
    }
    else if secbetweenDates > 0
    {
        print(secbetweenDates,"seconds")//seconds
    }
}