Sosigenes of Alexandria

Sosigenes of Alexandria was an ancient Greek astronomer and mathematician known for his work on calendar systems. He is most famous for advising Julius Caesar in 46 BCE on how to create a more accurate Roman calendar. Sosigenes proposed using a solar year—the time Earth takes to orbit the Sun—rather than the previous lunar-based calendar. His recommendations led to the Julian calendar, which better aligned the calendar year with the Earth's actual solar year, reducing errors and improving the accuracy of seasonal scheduling. His contributions helped shape the calendar system used in many parts of the world for centuries.