"Appear" and "change" are two different things in the DNS world. This is due to caching.
To know how long it will take you first need to know the TTL value that onlydomains.com has associated with the DNS entries.
Generally speaking, 12-24 hours is a good estimate for a "change", however that can inflate to 3 days to bee seen worldwide.
This issue is also completely outside of anything within dreamhosts control.