Determining the Bollywood movie that took the longest to make is a complex task as information on production timelines isn't always readily available. However, based on available information and estimations, "Mughal-e-Azam" (1960) is often considered the movie with the longest production time.
The film, directed by K. Asif, was in production for over five years, starting in 1954 and releasing in 1960.
The lengthy production was attributed to several factors:
* **Extensive sets and costumes:** The film featured elaborate sets and costumes, requiring meticulous craftsmanship and detailed attention to historical accuracy.
* **Technical challenges:** The film utilized innovative techniques for its time, including a large-scale chariot race sequence and complex lighting and sound effects.
* **Financial constraints:** The film faced financial difficulties, leading to delays and interruptions in production.
While "Mughal-e-Azam" is often cited as the movie with the longest production time, other films like "Hum Aapke Hain Koun..!" (1994) and "Sholay" (1975) also had extended production schedules due to various factors.
However, it's essential to acknowledge that production times can vary significantly, and accurate data isn't always available for every film.