Anno oxypetalum (literally "the year of the pointed petals") is a clock made of the flowers of night-blooming cacti, tracking the amount of light across one year. Each flower represents 10 minutes, each second approximately 2 days. Over the course of the piece the flowers fade in and out as the light ebbs and flows across the seasons. The timing of dawn and dusk is precisely accurate for London starting at the 2021 winter solstice. A third level of time is also incorporated into the work - when the piece is sold, the smart contract is programmed to start the video at the beginning of the season in which it was sold. The smart contract is able to accurately compute the solstices and equinoxes until the year 3000. It is inspired by plants' chrono-biological clocks, by which they bloom and close at fixed times of day. Plants behave this way regardless of external stimuli - a night-blooming cactus, for example, will only bloom at night, even if it is exposed to darkness during the daytime and light at night; a morning glory moved into permanent darkness will still flower in the mornings. The work call backs to Carl Linnaeus' idea of a horologium florae or floral clock, proposed in his Philosophia Botanica in 1751 after observing the phenomenon of certain flowers opening and closing at set times of the day, and harkens back to an earlier, medieval way of delineating time according to the amount of daylight present, before the advent of modern timekeeping.