This ring is based on the original sundial ring Queen Eleanor gave to her husband, Henry II of England in about 1152. On a cloudless day, hold the ring upright aligning one of the 3 reference lines straight up. Rotate the sun dial until the hole is next to the current date (month of the year and beginning/middle/end of the month) A beam of light illuminates the time on an inside clock scale. Calibrate by using the reference line that works with your latitude - northern cities will use a different line than southern ones. The 3 reference lines allow Daylight Savings Time adjustments as well. Made from VERY durable stainless steel, acid etched markings.