Question : How long are most people's visits to Dallas when they fly in from Kolkata?
Answer : Of course you're not most people, but if you were, you'd stay roughly 56 days.
Question : If your plans are flexible, have you considered changing your departure day?
Answer : The cheapest day to fly in December is Thursday. Being flexible with your travel days garners you even more savings during your booking.
Question : Are prices changing frequently for this route?
Answer : Flight prices for CCU to DFW fluctuate much more than the majority of routes. The further out you book a route, the more likely you are to save.