Strange Phenomenon

Carol and I saw this cut glass and prism ornament at a craft fair and bought it over 35 years ago. We never imagined that it would predict the first day of spring. We hung it in our triangle window and every year on the first day of spring it casts rainbow images on the wall. For 20 years it has been spot on accurate. On the first day of spring the house is aligned with the sun in just the right direction that it literally blooms rainbows. Some years it may be a day earlier or a day later but when spring arrives this casts rainbows on the ceiling. At its height it will move slightly and rainbows are in profusion and moving all over the front of the house.