Pope Julius II commissioned Michelangelo to paint the ceiling of the Sistine Chapel, and the work took from 1508 to 1512. The finished frescoes, with more than 300 figures, were revealed on the eve of All Saints' Day and shown to the public on the feast itself.
The pope chose the date because it was a major festival of the Church year. Among the scenes is The Creation of Adam.
Source: Artnet