Here is another interview where IGA discusses the timing of the game;
http://games.kikizo.com/features/koji-igarashi-interview-oct08-p2.aspIgarashi: The game itself doesn't indicate that it takes place at a specific point in the series timeline. However, the game happens during a time when the Belmont clan has vanished, along with their legendary whip, the Vampire Killer. But, Dracula is still around, so there are a lot of organizations are trying to bring him down, and a lot of effort and money are being expended. None of them have been successful save Ecclesia. Shanoa, the lead, is a member of this organization.
As for Belmonts who go missing, it could possibly be Richtor himself. If he goes missing, then his era is essentially over.
Apparently Nintendo power, claims the game takes place mid-1800s?
My guess the game takes place sometime between between 1820-1850 or so, maybe as late as 1870 (mid-1800s is a bit unspecific). If we knew when Shanoa was born, and when she joined the Ecclesia, it would help. But we don't have any exact dates. We at least know her age at the time of the game...? But that hardly helps us to understand when it takes place.