What are the dates for the seasonal changes in 2013?

Spring - Begins March 20, 2013 (spring equinox) at 7:02 am EDT.
Summer - Begins June 21, 2013 (summer solstice) at 1:04 am EDT.
Fall - Begins September 22, 2013 (Autumnal equinox) at 4:44 pm EDT.
Winter - Begins December 21, 2013 (winter solstice) at 12:11 pm EST.

Source: Chase's Calendar of Events 2013, pp.614.