a UILabel subclass that automatically updates elapsed time (eg: 1 month 2 weeks ago)

AutoUpdatingTimeElapsedLabel.swift

//
//  AutoUpdatingTimeElapsedLabel.swift
//
//  Created by Raunak Poddar on 03/09/19.
//

import UIKit

@objc class AutoUpdatingTimeElapsedLabel: UILabel {
    
    @objc static let ClockUpdateNotification = Notification.Name("ClockUpdateNotification")
    
    var eventTime: Date? {
        didSet {
            text = Date().timeElapsedString(sinceDate: eventTime)
        }
    }
    
    required init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)!
        self.commonInit()
        
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        self.commonInit()
    }
    
    func commonInit() {
        let center = NotificationCenter.default
        let mainQueue = OperationQueue.main
        text = Date().timeElapsedString(sinceDate: eventTime)
        center.addObserver(forName: AutoUpdatingTimeElapsedLabel.ClockUpdateNotification,
                           object: nil,
                           queue: mainQueue) { [weak self] (notification: Notification) in
                            if let date = notification.userInfo?["date"] as? Date {
                                self?.text = date.timeElapsedString(sinceDate: self?.eventTime)
                            }
        }
    }
    
}

Date+TimeElapsedString.swift

//
//  Date+TimeElapsedString.swift
//
//  Created by Raunak Poddar on 03/09/19.
//

import Foundation

extension Date {

    
    private static func elapsedString(forComponent component: Int,
                       subComponent: Int,
                       componentSingular: String,
                       componentPlural: String,
                       subComponentSingular: String,
                       subComponentPlural: String) -> String? {
        var str: String?
        if component > 1 && subComponent > 1 {
            str = "\(component) \(componentPlural) \(subComponent) \(subComponentPlural)"
        } else if component > 1  && subComponent == 1 {
            str = "\(component) \(componentPlural) \(subComponent) \(subComponentSingular)"
        } else if component > 1 {
            str = "\(component) \(componentPlural)"
        } else if component == 1 {
            str = "\(component) \(componentSingular)"
        }
        return str
    }
    

    func timeElapsedString(sinceDate since: Date?) -> String {
        
        if since == nil {
            return "??"
        }
        
        let dcs = Calendar.current.dateComponents([.year, .month, .weekOfMonth, .day, .hour, .minute, .second], from: since!, to: self)
        
//        return "\(dcs.year) \(dcs.month) \(dcs.day) \(dcs.hour) \(dcs.day)"
        
        var str: String?
        let year = dcs.year!
        let month = dcs.month!
        
        str = Date.elapsedString(forComponent: year,
                                 subComponent: month,
                                 componentSingular: "year",
                                 componentPlural: "years",
                                 subComponentSingular: "month",
                                 subComponentPlural: "months")
        
        
        if let str = str {
            return "\(str) ago"
        }
        
        let week = dcs.weekOfMonth!
        str = Date.elapsedString(forComponent: month,
                                 subComponent: week,
                                 componentSingular: "month",
                                 componentPlural: "months",
                                 subComponentSingular: "week",
                                 subComponentPlural: "weeks")
        if let str = str {
            return "\(str) ago"
        }
        
        let day = dcs.day!
        str = Date.elapsedString(forComponent: week,
                                 subComponent: day,
                                 componentSingular: "week",
                                 componentPlural: "weeks",
                                 subComponentSingular: "day",
                                 subComponentPlural: "days")
        if let str = str {
            return "\(str) ago"
        }
        
        let hour = dcs.hour!
        str = Date.elapsedString(forComponent: day,
                                 subComponent: hour,
                                 componentSingular: "day",
                                 componentPlural: "days",
                                 subComponentSingular: "hour",
                                 subComponentPlural: "hours")
        if let str = str {
            return "\(str) ago"
        }
        
        let min = dcs.minute!
        str = Date.elapsedString(forComponent: hour,
                                 subComponent: min,
                                 componentSingular: "hour",
                                 componentPlural: "hours",
                                 subComponentSingular: "minute",
                                 subComponentPlural: "minutes")
        if let str = str {
            return "\(str) ago"
        }
        
        let sec = dcs.second!
        str = Date.elapsedString(forComponent: min,
                                 subComponent: sec,
                                 componentSingular: "minute",
                                 componentPlural: "minutes",
                                 subComponentSingular: "second",
                                 subComponentPlural: "seconds")
        if let str = str {
            return "\(str) ago"
        }
        
        return "\(sec) seconds ago"
    }
}