Winter Solstice 2011

La Habra, CA, December 22, 2011 / — It’s official, Winter starts tonight in La Habra, California

La Habra, CA, December 22, 2011 / — Happy first day of Winter! Even though we’ve had really chilly mornings these past few days in La Habra, California and some colder than usual rain storms, Winter officially starts today and the Winter Solstice marks the shortest day of the year. The official time corresponds to 12:30AM Eastern Standard Time or 9:30PM Pacific Standard Time, Thursday, December 22.

Since mid-Summer, the days have been growing shorter, not just for La Habra, but everyplace in the Northern Hemisphere. Actually, “shorter days” is what people say — the days are still 24 hours long. What they really mean is since the Summer Solstice marking the longest day of the year, the number hours that sunlight shines for those of us North of the Equator is shorter by a few minutes each day, until 9:30PM tonight. After tonight, the number of hours that the Sun brightens our days grows longer by a few minutes each day, until the next Summer Solstice, in 2012. After that, the days begin growing shorter again.

This was an important event in ancient times, as the Winter Solstice marked the beginning of the coldest part of the year and people knew they needed to carefully manage there food supplies to survive.

In 46 BCE Julius Caesar decided to establish December 25 as the official date of the winter solstice of Europe. Although he must have meant well, his science was a little off, as the exact time of the Winter Solstice varies from year to year, depending on solar alignments, rotation periods that are not exactly 24 hours long and terrestrial events like the 8.9 magnitude earthquake in Japan, that shortened the day on Earth by 1.8 microseconds.