Using the same info that goes into your birth chart (your birth date, time, and place) plus the present date, a progressed birth chart calculates how far the planets have moved from their spot on your birth chart. For example, it's believed that the sun moves one degree forward on the Wheel of the Zodiac for every year after your birthday. And every sign occupies 30 degrees of the Wheel, so, by the time you hit your 30s, if not earlier, the sun could very well have moved onto the next sign on your progressed chart. By comparison, the moon will move on from your natal moon sign much sooner, as it changes signs about every three years in a progressed chart.