Which times of day are represented by Michelangelo’s sculptures for the Medici tombs?

For the Medici Chapel, Michelangelo created four allegorical sculptures representing the passage of time, which he associated with the inevitability of death. These figures are arranged in pairs on the sarcophagi of the two dukes:1

• Day and Night: These figures are located on the tomb of Giuliano, duke de Nemours. Day is depicted as a powerful, muscular male figure, while Night is represented as a female figure in a state of uneasy slumber.21
• Dawn and Dusk: These figures are located on the tomb of Lorenzo, duke di Urbino. Dawn is a female figure shown straining as if emerging into life, and Dusk is a male figure reclining in a state between sleep and waking.21

These sculptures serve as personifications of time's circular movement and are considered among the artist's most significant works.1