how to calculate how much time has passed when I registered such an item in the database

const getHoursOrMinutesAgo = (createdAtNanos) => {
    console.log(createdAtNanos)
    const now = moment();
    const createdAtMilliseconds = createdAtNanos / 1000000; 
    const createdAt = moment(createdAtMilliseconds);
        
    const duration = moment.duration(now.diff(createdAt));
        
    const hoursAgo = duration.hours();
    const minutesAgo = duration.minutes();
    const secondsAgo = duration.seconds();
    
    if (hoursAgo > 0) {
       return `${hoursAgo} hora(s) atrás`;
    } else if (minutesAgo > 0) {
       return `${minutesAgo} minuto(s) atrás`;
    } else {
       return `${secondsAgo} segundo(s) atrás`;
    }
};

I don’t know how to explain, please help me with that, i want just calculate how much time passed with a nanoseconds parameter