The above image is from jayhem’s photostream

The 2011 solstice comes on December 21 or 22, depending on your time zone. But the earliest sunsets for middle latitudes in the Northern Hemisphere are happening around now.

It seems paradoxical. At middle latitudes in the U.S. – and throughout the Northern Hemisphere – the earliest sunsets of the year come about two weeks before the solstice and the shortest day of the year.

Everything you need to know about the winter solstice

Analemma on globe shows sun's declination and difference (in minutes) between time as measured by the clock and sun.

Why isn’t the earliest sunset on the year’s shortest day? It’s because of the discrepancy between the clock and the sun. A clock ticks off exactly 24 hours from one noon to the next. But an actual day – as measured by the spin of the Earth, from what is called one “solar noon” to the next – rarely equals 24 hours exactly.

The next meteor shower is December 13 and 14, 2011

Solar noon is also called simply “midday.” It refers to that instant when the sun reaches its highest point for the day. At this time of year, the time period from one solar noon to the next is actually half a minute longer than 24 hours. Today, the sun reaches its noontime position at 11:52 a.m. local standard time. Two weeks from now – on the winter solstice – the sun will reach its noontime position around 11:59 a.m. That’s 7 minutes later than today.

The later clock time for solar noon also means a later clock time for sunrise and sunset. The table below helps to explain.

For Philadelphia, Pennsylvania

The exact date for the earliest sunset or earliest sunrise varies by latitude. At present, mid-temperate latitudes in the Northern Hemisphere have their earliest sunsets, while the Southern Hemisphere’s mid-temperate latitudes are waking up to their earliest sunrises. At latitudes closer to the equator, the earliest sunset or earliest sunrise has already come and gone. Closer to the Arctic and Antarctic Circles, the earliest sunset and earliest sunrise have yet to come.

Nearly sunset, as seen from Jamshedpur, India on September 28, 2011, via EarthSky Facebook friends Dolly Navina Lakra and Evewin Christon Lakra.

As you might have guessed, the latest sunrises and sunsets aren’t on the day of the solstice either.

Ten tips for watching the Geminid meteor shower

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So there’s variation in the exact dates, but the sequence is always the same for both hemispheres. First: earliest sunset before the winter solstice, the winter solstice itself, latest sunrise after the winter solstice. Half a year later: earliest sunrise before the summer solstice, the summer solstice itself, latest sunset.

Lunar eclipse for North America before sunrise December 10

The earliest and latest sunsets and sunrises are lovely phenomena that happen around every solstice. People around the world notice them and often ask about them.