Answer:
December 21
The 2009 Winter Solstice will occur at 9:47 a.m. on Monday, December 21, 2009. That will be the local time on the western coast of the continental United States.
In other parts of the world, however, local times may be different at that same moment. For example, in England at that moment, the local time will be 17:47 in the late afternoon.