We got the actual email with the interview time on 9/28 (DQ was 9/9). The initial interview date we received was for 11/28, however that was too late for us because my wife had been staying with me in the US on ESTA since 8/24 when my expat assignment in Japan finished and we left Japan together. The Tokyo Embassy does have a form online to request a change to the interview date - we explained the situation in detail and they gave us 10/19 as the earliest date they could.
I would note that for most people less than 3 weeks between the interview letter and the actual date might be too tight because you will also need to schedule the medical check and possibly receive additional vaccinations. For us this was not an issue as my wife completed the medical appointment back in July (prior to DQ) because we did not want any delay whatsoever.
