Answer:
4 years
It took 4 years (1503-1507) to paint it, although it was unfinished, it took another 3 years to complete, up to the year the painter died in 1519.
Step-by-step explanation:
For one thing, it's believed that da Vinci took about three years to paint The Last Supper, mostly due to the painter's notorious tendency to procrastinate. For another, stories of spiritual decay manifesting itself physically have long existed.Usually, it takes 2-3 sittings before I experience that definitive moment of “it's done.” Each sitting is approximately 3 hours. If the painting is small, I may be able to finish within 2 hours. Larger paintings take me longer.
Hope this helps!!