We spent three weeks in Delhi in order to attend our son's wedding. Even though that seems like a long time, the wedding and preparations for it took so much time we were unable to leave Delhi and were able to see only parts of the city. For example, we were unable to venture into old Delhi, ride on the subway, and saw only a few historical sites.
In case you are as confused as I was about the difference between "New Delhi" and "Delhi", here is a simple minded explanation. Delhi is a union territory. A union territory might be compared to a state in the U.S. but has less independence than a state. New Delhi is a small region in the union territory Delhi. It is the capital of both India and of the union territory Delhi.
Actually there was a fourth day that happened before we arrived and is not covered here.