In astrology, the transit of the Sun over the position it occupies in ones natal chart. Since the cycle of the sun is one solar year and the western calendar is based on it, it will often fall on ones birthday. The return, as with any other planetary return, occurs when the Sun reaches the exact, preferably to the second of a degree, position it was in when the person was born.
Depending on the year and time of birth, the solar return may coincide with ones birth date or be off by a day (before or after) because the discrepancy between the calendar year and solar year can reach as much as 18 hours. In almost all cases, ones solar return will coincide with the calendar anniversary of ones birth only in one to three of every four years.
Solar returns are considered significant events and often a chart is cast based on the exact time of the solar return. This chart is read to provide predictions and guidance for the coming year and may be superimposed on the person's natal chart to provide a composite chart that's used for a more detailed reading.