如果你的目的是获得两个日期之间的确切天数，你可以这样解决这个问题:

// Assuming that firstDate and secondDate are defined
// ...

var calendar: NSCalendar = NSCalendar.currentCalendar()

// Replace the hour (time) of both dates with 00:00
let date1 = calendar.startOfDayForDate(firstDate)
let date2 = calendar.startOfDayForDate(secondDate)

let flags = NSCalendarUnit.DayCalendarUnit
let components = calendar.components(flags, fromDate: date1, toDate: date2, options: nil)

components.day  // This will return the number of day(s) between dates

如果有人需要显示所有的时间单位，如“小时分秒”，而不仅仅是“小时”。假设两个日期的时差是1小时59分20秒。该功能将显示“1h 59m 20s”。

下面是我的Objective-C代码:

extension NSDate {

    func offsetFrom(date: NSDate) -> String {

        let dayHourMinuteSecond: NSCalendarUnit = [.Day, .Hour, .Minute, .Second]
        let difference = NSCalendar.currentCalendar().components(dayHourMinuteSecond, fromDate: date, toDate: self, options: [])

        let seconds = "\(difference.second)s"
        let minutes = "\(difference.minute)m" + " " + seconds
        let hours = "\(difference.hour)h" + " " + minutes
        let days = "\(difference.day)d" + " " + hours

        if difference.day    > 0 { return days }
        if difference.hour   > 0 { return hours }
        if difference.minute > 0 { return minutes }
        if difference.second > 0 { return seconds }
        return ""
    }

}

在Swift 3+中:

extension Date {

    func offsetFrom(date: Date) -> String {

        let dayHourMinuteSecond: Set<Calendar.Component> = [.day, .hour, .minute, .second]
        let difference = NSCalendar.current.dateComponents(dayHourMinuteSecond, from: date, to: self)

        let seconds = "\(difference.second ?? 0)s"
        let minutes = "\(difference.minute ?? 0)m" + " " + seconds
        let hours = "\(difference.hour ?? 0)h" + " " + minutes
        let days = "\(difference.day ?? 0)d" + " " + hours

        if let day = difference.day, day          > 0 { return days }
        if let hour = difference.hour, hour       > 0 { return hours }
        if let minute = difference.minute, minute > 0 { return minutes }
        if let second = difference.second, second > 0 { return seconds }
        return ""
    }

}

  func dateDiff(dateStr:String) -> String {
        var f:NSDateFormatter = NSDateFormatter()
        f.timeZone = NSTimeZone.localTimeZone()
        f.dateFormat = "yyyy-M-dd'T'HH:mm:ss.SSSZZZ"
        
        var now = f.stringFromDate(NSDate())
        var startDate = f.dateFromString(dateStr)
        var endDate = f.dateFromString(now)
        var calendar: NSCalendar = NSCalendar.currentCalendar()
        
        let calendarUnits = NSCalendarUnit.CalendarUnitWeekOfMonth | NSCalendarUnit.CalendarUnitDay | NSCalendarUnit.CalendarUnitHour | NSCalendarUnit.CalendarUnitMinute | NSCalendarUnit.CalendarUnitSecond
        let dateComponents = calendar.components(calendarUnits, fromDate: startDate!, toDate: endDate!, options: nil)
        
        let weeks = abs(dateComponents.weekOfMonth)
        let days = abs(dateComponents.day)
        let hours = abs(dateComponents.hour)
        let min = abs(dateComponents.minute)
        let sec = abs(dateComponents.second)
        
        var timeAgo = ""

        if (sec > 0){
            if (sec > 1) {
                timeAgo = "\(sec) Seconds Ago"
            } else {
                timeAgo = "\(sec) Second Ago"
            }
        }
        
        if (min > 0){
            if (min > 1) {
                timeAgo = "\(min) Minutes Ago"
            } else {
                timeAgo = "\(min) Minute Ago"
            }
        }
        
        if(hours > 0){
            if (hours > 1) {
                timeAgo = "\(hours) Hours Ago"
            } else {
                timeAgo = "\(hours) Hour Ago"
            }
        }
        
        if (days > 0) {
            if (days > 1) {
                timeAgo = "\(days) Days Ago"
            } else {
                timeAgo = "\(days) Day Ago"
            }
        }
        
        if(weeks > 0){
            if (weeks > 1) {
                timeAgo = "\(weeks) Weeks Ago"
            } else {
                timeAgo = "\(weeks) Week Ago"
            }
        }
        
        print("timeAgo is===> \(timeAgo)")
        return timeAgo;
    }

这是一个较短的版本:基本上我现在尝试获得post时间戳与Date()之间的差异。

// MARK: - UPDATE Time Stamp
static func updateTimeStampPost(postTimeStamp: Date?, _ completion: (_ finalString: String?) -> Void) {
    // date in the current state
    let date = Date()
    let dateComponentFormatter = DateComponentsFormatter()

    // change the styling date, wether second minute or hour
    dateComponentFormatter.unitsStyle = .abbreviated
    dateComponentFormatter.allowedUnits = [.second, .minute, .hour, .day, .weekOfMonth]
    dateComponentFormatter.maximumUnitCount = 1

    // return the date new format as a string in the completion
    completion(dateComponentFormatter.string(from: postTimeStamp!, to: date))
}

使用以下代码:

let registrationDateString = "2008-10-06 00:00:00"
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd hh:mm:ss"
    if let registrationDate = dateFormatter.date(from: registrationDateString) {
        let currentDate = Date()
        let dateDifference = Calendar.current.dateComponents([.day, .month, .year],
                                                               from: registrationDate,
                                                               to: currentDate)
        print("--------------------- Result: \(dateDifference.year ?? 0) years \(dateDifference.month ?? 0) months and \(dateDifference.day ?? 0) days")
    } else {
        print("--------------------- No result")
    }

结果:10年1个月18天

——>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
    }
}