RelativeDate.swift

func relativeDateString(date: NSDate) -> String {
    
    let components: Array<(Int, (Int) -> String)> = [
        (60 * 60 * 24 * 365, { x in "\(x) anni fa" }),
        (60 * 60 * 24 *  30, { x in "\(x) mesi fa" }),
        (60 * 60 * 24      , { x in "\(x) giorni fa" }),
        (60 * 60           , { x in "\(x) ore fa" }),
        (60                , { x in "\(x) minuti fa" })
    ]
    
    let timeInterval = Int(NSDate().timeIntervalSinceDate(date))
    
    for (secondsPerComponent, formatString) in components {
        let componentUnits = timeInterval / secondsPerComponent
        
        if componentUnits != 0 {
            return formatString(componentUnits)
        }
    }
    
    return "alcuni secondi fa"
}

RelativeDate2.swift

func relativeDateString(date: NSDate) -> String {
        
        let calendar = NSCalendar.currentCalendar()
        let components = calendar.components([.WeekOfYear, .Day, .Hour, .Minute], fromDate: date, toDate: NSDate(), options: [])
        
        if components.weekOfYear > 0 { // More than 7 days
        
            return Utility.dateFormattedEuropeMode(date)
        
        } else if components.day > 0 { // This week
        
            if components.day > 1 { // More than 1 day
            
                return "\(components.day) \(Utility.localizedString("DAYS_AGO"))"
            
            } else { // Yesterday
            
                return Utility.localizedString("YESTERDAY")
            
            }
            
        } else { // Today
            
            if components.hour > 1 { // From 2 to 23 hours
            
                return "\(components.hour) \(Utility.localizedString("HOURS_AGO"))"
            
            } else {
            
                if components.hour == 1 { // 1 hour
                
                    return "\(components.hour) \(Utility.localizedString("HOUR_AGO"))"
                
                } else {
                
                    if components.minute > 5 { // From 5 to 59 minutes
                    
                        return "\(components.minute) \(Utility.localizedString("MINUTES_AGO"))"
                    
                    } else { // Less than 5 minutes
                    
                        return Utility.localizedString("NOW")
                    
                    }
                
                }
            
            }
        
        }
        
    }