The winter solstice in the Northern Hemisphere in 2011 is on December 22.
But if I look at the sunset times for a location such as Washington, DC on the USNO site, the sunset time starts reversing much earlier (around December 6th).
Shouldn't the sunset time start reversing (from earlier to later) on the same date as the solstice?
Update:
Omega Centauri's explanation is correct.