This class can be used to get formatted Date Time as ago

DateTimeAsAgo.swift

//
//  DateTimeAsAgo.swift
//  DateTimeAsAgo
//
//  Created by Arpit Jain on 14/05/18.
//  Copyright (c) 2018 Arpit Jain . All rights reserved.
//

import Foundation

extension Date{
    
    /// Use this method to to get formatted Date Time as ago
    ///
    /// - Parameters:
    ///   - fromDate: Pass date from which you want to get fromatted date time as ago.
    
    public func getDateTimeAsAgo(fromDate: Date = Date()) -> String {
        
        let secondsFromDate = fromDate.secondsFrom(date: self)
        
        if secondsFromDate < 60 {
            return secondsFormatter()
        }
        
        let minutesFromDate = fromDate.minutesFrom(date: self)
        if minutesFromDate < 60 {
            return minutesFormatter(minutes: minutesFromDate)
        }
        
        let hoursFromDate = fromDate.hoursFrom(date: self)
        if hoursFromDate < 24 {
            return hoursFormatter(hours: hoursFromDate)
        }
        
        let daysFromDate = fromDate.daysFrom(date: self)
        switch daysFromDate {
        case 1:
            return yesterdayFormatter()
        case 2...6:
            return daysFormatter(days: daysFromDate)
        default:
            break
        }
        
        let weeksFromDate = fromDate.weeksFrom(date: self)
        
        let monthsFromDate = fromDate.monthsFrom(date: self)
        switch monthsFromDate {
        case 0:
            return weeksFormatter(weeks: weeksFromDate)
        case 1...11:
            return monthsFormatter(months: monthsFromDate)
        default:
            break
        }
        
        let yearsFromDate = fromDate.yearsFrom(date: self)
        return yearsFormatter(years: yearsFromDate)
    }
}

// MARK: Formatter functions

func classicFormatterAgo(quantity: Int, unit: String) -> String {
    
    var formattedString = "\(quantity) \(unit)"
    if quantity > 1 {
        formattedString += "s"
    }
    formattedString += " ago"
    return formattedString
    
}

func secondsFormatter() -> String {
    return "Just now"
}

func minutesFormatter(minutes: Int) -> String {
    return classicFormatterAgo(quantity: minutes, unit: "minute")
}

func hoursFormatter(hours: Int) -> String {
    return classicFormatterAgo(quantity: hours, unit: "hour")
}

func yesterdayFormatter() -> String {
    return "Yesterday"
}

func daysFormatter(days: Int) -> String {
    return classicFormatterAgo(quantity: days, unit: "day")
}

func weeksFormatter(weeks: Int) -> String {
    return classicFormatterAgo(quantity: weeks, unit: "week")
}

func monthsFormatter(months: Int) -> String {
    return classicFormatterAgo(quantity: months, unit: "month")
}

func yearsFormatter(years: Int) -> String {
    return classicFormatterAgo(quantity: years, unit: "year")
}

// MARK: Extension of Date

private extension Date {
    
    func yearsFrom(date:Date) -> Int{
        return Calendar.current.dateComponents([.year], from: date, to: self).year!
    }
    
    func monthsFrom(date:Date) -> Int{
        return Calendar.current.dateComponents([.month], from: date, to: self).month!
    }
    
    func weeksFrom(date:Date) -> Int{
        return Calendar.current.dateComponents([.weekOfYear], from: date, to: self).weekOfYear!
    }
    
    func daysFrom(date:Date) -> Int{
        return Calendar.current.dateComponents([.day], from: date, to: self).day!
    }
    
    func hoursFrom(date:Date) -> Int{
        return Calendar.current.dateComponents([.hour], from: date, to: self).hour!
    }
    
    func minutesFrom(date:Date) -> Int{
        return Calendar.current.dateComponents([.minute], from: date, to: self).minute!
    }
    
    func secondsFrom(date:Date) -> Int{
        return Calendar.current.dateComponents([.second], from: date, to: self).second!
    }
}