It takes Cruithne about 364 days to orbit the sun, almost the same amount of time it takes for the Earth to complete it's orbit of the sun. Because of this, it appears that the Earth and Cruithne follow each other around the sun and that is why it is sometimes erroneously referred to as Earth's second moon.
It takes slightly less than a year for Cruithne to complete it's path around the sun, which means Earth 'falls behind' a little more each year. Eventually, after many years, Earth would have fallen behind so much that Cruithne will be catching up from behind.
When Cruithne does catch up, it will make a series of annual close approaches to the Earth and gravitationally exchange orbital energy with Earth. This will alter Cruithne's orbit by a little over half a million kilometers and Earth's orbit will altered by about 1.3 centimeters. This will mean that it will take us a bit more than a year to orbit the sun.
