The premise for your visit may be relevant.
IMO if going for say a week’s vacation then it should not be a big problem.
On the other hand if going for a conference (say week long and commencing 11/1/17) then it probably would be a big problem because you are clearly not going to make that in time, and the premise for your visa is no longer valid. That being so you would need a new premise and hence a new assessment and hence a new application.
See also.
Equivalent issue for Schengen.
Credit:stackoverflow.com‘
4 Mar, 2024
5 Mar, 2024
4 Mar, 2024