It usually takes 24-48 hours for a domain to fully replicate changes,
additions, or deletions across all name servers. For you to see the
effects, however, all depends on your ISP. Updates my be within
minutes for your neighbor, but may take up to a week for you or
vice-versa. The DNS information is updated on 'root servers' all
over the globe and they are not update all at one time.
The reason for this is the name servers for your ISP update at different
times. For various ISPs it is quite possible for DNS take a week or
more to update because they have cached the old dns information
to save time and resources on their equipment. There is nothing
We can do about that.