Sto cercando di ottenere la differenza tra la data corrente come NSDate()e una data da un PHP time();chiamata, ad esempio: NSDate(timeIntervalSinceReferenceDate: 1417147270). Come posso fare per ottenere la differenza temporale tra le due date. Mi piacerebbe avere una funzione che confronta le due date e if(seconds > 60)quindi restituisce minuti, if(minutes > 60)ore di if(hours > 24)ritorno e giorni di ritorno e così via.

Come devo procedere?

EDIT: l'attuale risposta accettata ha fatto esattamente quello che volevo fare. Lo consiglio per un facile utilizzo per ottenere il tempo tra due date nel modulo time()utilizzato dalla funzione PHP . Se non hai familiarità con PHP, questo è il tempo in secondi dal 1 ° gennaio 1970. Questo è utile per un backend in PHP. Se forse stai usando un backend come NodeJS, potresti prendere in considerazione alcune delle altre opzioni che troverai di seguito.

Xcode 8.3 • Swift 3.1 o successivo

Puoi utilizzare Calendar per aiutarti a creare un'estensione per eseguire i calcoli della data come segue:

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 ""
    }
}

Utilizzo di Formatter componenti data

let dateComponentsFormatter = DateComponentsFormatter()
dateComponentsFormatter.allowedUnits = [.year,.month,.weekOfMonth,.day,.hour,.minute,.second]
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"

Se qualcuno deve visualizzare tutte le unità di tempo, ad esempio "ore minuti secondi", non solo "ore". Diciamo che la differenza di tempo tra due date è di 1 ora 59 minuti e 20 secondi. Questa funzione visualizzerà "1h 59m 20s".

Ecco il mio codice Objective-C:

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 ""
    }

}

In Swift 3+:

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 ""
    }

}

Tu chiedi:

Vorrei avere una funzione che confronta le due date e se (secondi> 60) restituisce minuti, se (minuti> 60) ore di ritorno e se (ore> 24) giorni di ritorno e così via.

Suppongo che stai cercando di creare una rappresentazione in forma di stringa del tempo trascorso tra due date. Invece di scrivere il tuo codice per farlo, Apple ha già una classe progettata per farlo proprio. Vale a dire, utilizzare DateComponentsFormatter, impostare allowedUnitssu qualsiasi valore abbia senso per l'app, impostare unitsStylesu ciò che si desidera (ad esempio .full) e quindi chiamarestring(from:to:) .

Ad esempio in Swift 3:

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)

Questo localizzerà anche la stringa appropriata per il dispositivo in questione.

Oppure, in Swift 2.3:

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)

Se stai cercando i valori numerici effettivi, basta usare dateComponents. Ad esempio in Swift 3:

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

Oppure, in Swift 2.3:

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

combinata Extension + DateComponentsFormatter dalla risposta di @ leo-dabus

Xcode 8.3 • Swift 3.1

extension DateComponentsFormatter {
    func difference(from fromDate: Date, to toDate: Date) -> String? {
        self.allowedUnits = [.year,.month,.weekOfMonth,.day]
        self.maximumUnitCount = 1
        self.unitsStyle = .full
        return self.string(from: fromDate, to: toDate)
    }
}

let dateComponentsFormatter = DateComponentsFormatter()
dateComponentsFormatter.difference(from: Date(), to: Date(timeIntervalSinceNow: 4000000)) // "1 month"

   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;
        }

Ho aggiunto una versione "lunga" alla risposta di Leo Dabus nel caso in cui tu voglia avere una stringa che dica qualcosa del tipo "2 settimane fa" anziché solo "2w" ...

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([.weekOfYear], from: date, to: self).weekOfYear ?? 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 ""
    }

    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 ""
    }

}

-> Usa questo per trovare l'intervallo di tempo tra due date in Swift (con due stringhe).

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
    }
}

Codice leggermente modificato per Swift 3.0

let calendar = NSCalendar.current as NSCalendar

// Replace the hour (time) of both dates with 00:00
let date1 = calendar.startOfDay(for: startDateTime)
let date2 = calendar.startOfDay(for: endDateTime)

let flags = NSCalendar.Unit.day
let components = calendar.components(flags, from: date1, to: date2, options: [])

return components.day!

Swift 5.1 • iOS 13

Puoi usare RelativeDateFormatter che è stato introdotto da Apple in iOS 13.

let exampleDate = Date().addingTimeInterval(-15000)

let formatter = RelativeDateTimeFormatter()
formatter.unitsStyle = .full
let relativeDate = formatter.localizedString(for: exampleDate, relativeTo: Date())

print(relativeDate) // 4 hours ago

Vedi Come mostrare una data e un'ora relative usando RelativeDateTimeFormatter .

Se il tuo scopo è ottenere il numero esatto del giorno tra due date, puoi aggirare questo problema in questo modo:

// 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

Con Swift 3, in base alle tue esigenze, puoi scegliere uno dei due seguenti modi per risolvere il tuo problema.

1. Visualizza la differenza tra due date per l'utente

Puoi usare a DateComponentsFormatterper creare stringhe per l'interfaccia della tua app. DateComponentsFormatterha una maximumUnitCountproprietà con la seguente dichiarazione:

var maximumUnitCount: Int { get set }

Utilizzare questa proprietà per limitare il numero di unità visualizzate nella stringa risultante. Ad esempio, con questa proprietà impostata su 2, anziché "1h 10m, 30s", la stringa risultante sarebbe "1h 10m". Utilizzare questa proprietà quando si è limitati allo spazio o si desidera arrotondare i valori all'unità grande più vicina.

Impostando maximumUnitCountil valore su 1, si garantisce di visualizzare la differenza in una solaDateComponentsFormatter unità (anni, mesi, giorni, ore o minuti).

Il codice Playground di seguito mostra come visualizzare la differenza tra due date:

import Foundation

let oldDate = Date(timeIntervalSinceReferenceDate: -16200)
let newDate = Date(timeIntervalSinceReferenceDate: 0)

let dateComponentsFormatter = DateComponentsFormatter()
dateComponentsFormatter.allowedUnits = [NSCalendar.Unit.year, .month, .day, .hour, .minute]
dateComponentsFormatter.maximumUnitCount = 1
dateComponentsFormatter.unitsStyle = DateComponentsFormatter.UnitsStyle.full
let timeDifference = dateComponentsFormatter.string(from: oldDate, to: newDate)

print(String(reflecting: timeDifference)) // prints Optional("5 hours")

Si noti che DateComponentsFormatterarrotonda il risultato. Pertanto, una differenza di 4 ore e 30 minuti verrà visualizzata come 5 ore .

Se devi ripetere questa operazione, puoi refactificare il tuo codice:

import Foundation

struct Formatters {

    static let dateComponentsFormatter: DateComponentsFormatter = {
        let dateComponentsFormatter = DateComponentsFormatter()
        dateComponentsFormatter.allowedUnits = [NSCalendar.Unit.year, .month, .day, .hour, .minute]
        dateComponentsFormatter.maximumUnitCount = 1
        dateComponentsFormatter.unitsStyle = DateComponentsFormatter.UnitsStyle.full
        return dateComponentsFormatter
    }()

}

extension Date {
    
    func offset(from: Date) -> String? {
        return Formatters.dateComponentsFormatter.string(from: oldDate, to: self)
    }
    
}

let oldDate = Date(timeIntervalSinceReferenceDate: -16200)
let newDate = Date(timeIntervalSinceReferenceDate: 0)

let timeDifference = newDate.offset(from: oldDate)
print(String(reflecting: timeDifference)) // prints Optional("5 hours")

2. Ottieni la differenza tra due date senza formattazione

Se non è necessario visualizzare all'utente la formattazione della differenza tra due date, è possibile utilizzare Calendar. Calendarha un metodo dateComponents(_:from:to:)che ha la seguente dichiarazione:

func dateComponents(_ components: Set<Calendar.Component>, from start: Date, to end: Date) -> DateComponents

Restituisce la differenza tra due date.

Il codice Playground di seguito che utilizza dateComponents(_:from:to:)mostra come recuperare la differenza tra due date restituendo la differenza in un solo tipo di Calendar.Component(anni, mesi, giorni, ore o minuti).

import Foundation

let oldDate = Date(timeIntervalSinceReferenceDate: -16200)
let newDate = Date(timeIntervalSinceReferenceDate: 0)

let descendingOrderedComponents = [Calendar.Component.year, .month, .day, .hour, .minute]
let dateComponents = Calendar.current.dateComponents(Set(descendingOrderedComponents), from: oldDate, to: newDate)
let arrayOfTuples = descendingOrderedComponents.map { ($0, dateComponents.value(for: $0)) }

for (component, value) in arrayOfTuples {
    if let value = value, value > 0 {
        print(component, value) // prints hour 4
        break
    }
}

Se devi ripetere questa operazione, puoi refactificare il tuo codice:

import Foundation

extension Date {
    
    func offset(from: Date) -> (Calendar.Component, Int)? {
        let descendingOrderedComponents = [Calendar.Component.year, .month, .day, .hour, .minute]
        let dateComponents = Calendar.current.dateComponents(Set(descendingOrderedComponents), from: from, to: self)
        let arrayOfTuples = descendingOrderedComponents.map { ($0, dateComponents.value(for: $0)) }
        
        for (component, value) in arrayOfTuples {
            if let value = value, value > 0 {
                return (component, value)
            }
        }
        
        return nil
    }

}

let oldDate = Date(timeIntervalSinceReferenceDate: -16200)
let newDate = Date(timeIntervalSinceReferenceDate: 0)

if let (component, value) = newDate.offset(from: oldDate) {
    print(component, value) // prints hour 4
}

In Swift 2.2

    /// Returns the amount of years from another date
func years(fromdate: NSDate) -> Int {
    return NSCalendar.currentCalendar().components([.Year], fromDate: fromdate, toDate: NSDate(), options: []).year ?? 0
}
/// Returns the amount of months from another date
func months(fromdate: NSDate) -> Int {
    return NSCalendar.currentCalendar().components([.Month], fromDate: fromdate, toDate: NSDate(), options: []).month ?? 0
}
/// Returns the amount of weeks from another date
func weeks(fromdate: NSDate) -> Int {
    return NSCalendar.currentCalendar().components([.WeekOfYear], fromDate: fromdate, toDate: NSDate(), options: []).weekOfYear ?? 0
}
/// Returns the amount of days from another date
func days(fromdate: NSDate) -> Int {
    return NSCalendar.currentCalendar().components([.Day], fromDate: fromdate, toDate: NSDate(), options: []).day ?? 0
}
/// Returns the amount of hours from another date
func hours(fromdate: NSDate) -> Int {
    return NSCalendar.currentCalendar().components([.Hour], fromDate: fromdate, toDate: NSDate(), options: []).hour ?? 0
}
/// Returns the amount of minutes from another date
func minutes(fromdate: NSDate) -> Int {
    return NSCalendar.currentCalendar().components([.Minute], fromDate: fromdate, toDate: NSDate(), options: []).minute ?? 0
}
/// Returns the amount of seconds from another date
func seconds(fromdate: NSDate) -> Int {
    return NSCalendar.currentCalendar().components(.Second, fromDate: fromdate, toDate: NSDate(), options: []).second ?? 0
}

Una piccola aggiunta alla risposta di Leo Dabus per fornire le versioni plurali ed essere più leggibile dall'uomo.

Swift 3

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)   == 1 { return "\(years(from: date)) year"   } else if years(from: date)   > 1 { return "\(years(from: date)) years"   }
        if months(from: date)  == 1 { return "\(months(from: date)) month"  } else if months(from: date)  > 1 { return "\(months(from: date)) month"  }
        if weeks(from: date)   == 1 { return "\(weeks(from: date)) week"   } else if weeks(from: date)   > 1 { return "\(weeks(from: date)) weeks"   }
        if days(from: date)    == 1 { return "\(days(from: date)) day"    } else if days(from: date)    > 1 { return "\(days(from: date)) days"    }
        if hours(from: date)   == 1 { return "\(hours(from: date)) hour"   } else if hours(from: date)   > 1 { return "\(hours(from: date)) hours"   }
        if minutes(from: date) == 1 { return "\(minutes(from: date)) minute" } else if minutes(from: date) > 1 { return "\(minutes(from: date)) minutes" }
        return ""
    }
}

Questa è la versione più breve: fondamentalmente cerco di ottenere la differenza tra il timestamp post con il Date()now.

// 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))
}

Ecco la mia risposta per le risposte Swift 3 sopra. Questo è attuale a partire da novembre 2016, la versione Xcode era 8.2 Beta (8C23). Ho usato alcuni dei suggerimenti Sagar ed Emin sopra e talvolta ho dovuto lasciare che Xcode completasse automaticamente per suggerire la sintassi. Sembrava che la sintassi fosse davvero cambiata in questa versione beta. buyDateHo ricevuto da un DatePicker:

let calendar = NSCalendar.current as NSCalendar
let currentDate = Date()
let date1 = calendar.startOfDay(for: buyDate!)
let date2 = calendar.startOfDay(for: currentDate)      
let flags = NSCalendar.Unit.day
let components = calendar.components(flags, from: date1, to: date2)
NSLog(" day= \(components.day)")

Per XCode versione 8.3.3 e 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)")

Qualche aggiunta nella risposta jose920405 per renderla compatibile con Swift 3.0 e versioni successive

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 minutes < 2 {
            timeAgo = "Hour Ago"
        }
        else{
            timeAgo = "\(hours) Hours Ago"
        }
    }

    if (days > 0) {
        if minutes < 2 {
            timeAgo = "Day Ago"
        }
        else{
            timeAgo = "\(days) Days Ago"
        }
    }

    if(months > 0){
        if minutes < 2 {
            timeAgo = "Month Ago"
        }
        else{
            timeAgo = "\(months) Months Ago"
        }
    }

    if(years > 0){
        if minutes < 2 {
            timeAgo = "Year Ago"
        }
        else{
            timeAgo = "\(years) Years Ago"
        }
    }

    DLog("timeAgo is ===> \(timeAgo)")
    return timeAgo;
}

Usa questo codice:

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")
    }

L'output è: Risultato: 10 anni 1 mese e 18 giorni

import Foundation

extension DateComponents {

    func dateComponentsToTimeString() -> String {

        var hour = "\(self.hour!)"
        var minute = "\(self.minute!)"
        var second = "\(self.second!)"

        if self.hour! < 10 { hour = "0" + hour }
        if self.minute! < 10 { minute = "0" + minute }
        if self.second! < 10 { second = "0" + second }

        let str = "\(hour):\(minute):\(second)"
        return str
    }

}

extension Date {

    func offset(from date: Date)-> DateComponents {
        let components = Set<Calendar.Component>([.second, .minute, .hour, .day, .month, .year])
        let differenceOfDate = Calendar.current.dateComponents(components, from: date, to: self)
        return differenceOfDate
    }
}

Uso:

var durationString: String {
        return self.endTime.offset(from: self.startTime).dateComponentsToTimeString()
    }