This questions can trip you up, so be careful! If you state a time period that is too short, you could be perceived as being unrealistic or unaware of company / department / project specifics on which to base an accurate estimate. Stating too long a time period could rule you out. One response might be: “I want to make a positive contribution as soon as possible, and my abilities as ____ and skills at ____ (relevant to this job) would enable me to get my feet wet quickly. I am driven and motivated to contribute to the success of department and the company” Keep your answers focused and relevant to the goals of the company and the work you’ll be expected to perform.