Opera Astrologica Perpetua Ridotta Secondo La Nuova Riforma Dell' Anno
Antonio Carrarino (fl. 1581-1608)
Astrological calendar
Rome, 1581
Engraving with etching
WOP-140

This work seems to be a perpetual calendar of planetary hours. Each large circular diagram represents a month; the smaller circles describe the astrological and astronomical specifications of the planets. Planetary hours as derived from Egyptian astronomy, pair each hour in the twenty-four hour cycle with a different planet (Saturn, Jupiter, Mars, the Sun, Venus, Mercury, and the Moon) resulting in a seven day rotation. Each day was named after the planet which governed the first hour; this system is still seen in the modern day names of the week in most European languages.

The title of the work indicates that the purpose of this chart was a recalculation of planetary hours, produced in anticipation of the Gregorian reformation of the calendar in 1582. In addition to the planetary hours, the center of each large circle shows the hours of darkness and daylight during each month. Thus, the winter months are allotted the least amount of daylight, while the summer months have the most. The hours shown are "Italian" hours with the first hour of the day commencing at dusk rather than midnight. The chart also features a central volvelle (a diagram with a movable pointer) to be used for finding ascending and descending celestial signs.