Perpetal luni-solar calendar, hijri-gregorian date converter and moon phase predictor.

This circular converter bridges the hijri and Gregorian calendars while tracking lunar phases—a practical tool born from an astronomer's need to navigate both timekeeping systems. The device translates dates between calendars with precision within one or two days and identifies moon phases for any Gregorian date, operating on a tabular Islamic calendar model. Instructions are printed on the back, and the zodiac markers serve an astronomical function for tracking seasons rather than divination.