Take a peek at your calendar, or even tune into the national news stations, and they'll likely talk about how winter begins on Thursday, December 22. But, did you know that here in Seattle, winter actually starts a day earlier?
(No fair joking that it starts two months earlier...)
The winter solstice officially occurs at 5:30 a.m. on December 22nd on "UTC" time (which is the old Greenwich Mean Time; also known as "Zulu" or 'Z' time to the military and weather world). However you name the time zone, it's 8 hours ahead of our Pacific Time Zone.
So do the math, and you find that winter actually begins in Seattle at 9:30 p.m. on Wednesday, December 21.
Most calendars and the like use UTC/GMT/Z time to calculate when such things like the seasons begin or the moon goes full. So when those times are in the early morning hours, it's actually the night before in Seattle.
But it works the other way too -- in 2013, summer will start a day early in Seattle!
(We'll see if Mother Nature figures it out.)