Get time string from a date

Date.swift

func timeStringFromDate(_ date: Date) -> String? {
    let dateComponents = Calendar.current.dateComponents([.year, .month, .day, .hour, .minute, .second], from: date)

    let dateTimestamp = date.timeIntervalSince1970
    let currentDateTimestamp = Date().timeIntervalSince1970

    let diff: TimeInterval = currentDateTimestamp - dateTimestamp

    guard diff >= 0 else {
        return nil
    }

    let yearTimeInterval: TimeInterval = 31536000
    let monthTimeInterval: TimeInterval = 2678400
    let dayTimeInterval: TimeInterval = 86400
    let hourTimeInterval: TimeInterval = 3600
    let minuteTimeInterval: TimeInterval = 60
    let secondTimeInterval: TimeInterval = 1

    if diff > yearTimeInterval {
        let years = Int(diff / yearTimeInterval)
        return "\(years) year\(years > 1 ? "s" : "") ago"
    }

    if diff > monthTimeInterval {
        let months = Int(diff / monthTimeInterval)
        return "\(months) month\(months > 1 ? "s" : "") ago"
    }

    if diff > dayTimeInterval {
        let days = Int(diff / dayTimeInterval)
        return "\(days) day\(days > 1 ? "s" : "") ago"
    }

    if diff > hourTimeInterval {
        let hours = Int(diff / hourTimeInterval)
        return "\(hours) hour\(hours > 1 ? "s" : "") ago"
    }

    if diff > minuteTimeInterval {
        let minutes = Int(diff / minuteTimeInterval)
        return "\(minutes) minute\(minutes > 1 ? "s" : "") ago"
    }

    if diff > secondTimeInterval {
        let seconds = Int(diff)
        return "\(seconds) second\(seconds > 1 ? "s" : "") ago"
    }

    return "just now"
}