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Seasoned Experts Got It Right

TIMES STAFF WRITER

Contrary to popular belief, summer arrived Thursday.

Astronomers officially marked its arrival at 7:24 p.m. Pacific Daylight Time. But don’t try to convince the publishers of certain books of facts.

Webster’s Dictionary says summer solstice--the longest day of the year, which marks the start of summer--falls on June 21 or 22, not June 20.

The World Book Encyclopedia has June 20 or 21 on its calendar.

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Well, which is it?

John Mosley, an astronomer at the Griffith Observatory, said astronomers aren’t the ones who are confused.

“One reason you have a day’s variation is that there are two days in progress at any given time on the planet,” Mosley said, offering a dose of enlightenment, if you can understand it.

Mosley explained that with the differences in time zones around the world, the exact time for summer to start can vary by a day or two. Astronomers, he said, rely on Greenwich time, the mean solar time of the meridian at Greenwich, England, used as the basis for standard time throughout most of the world.

Another reason summer arrived on June 20 is that 1996 is a leap year. Each year really has 365 1/4 days. That extra quarter, or six hours, adds up every four years to one full day, which changes the date of summer.

Essentially, the arrival of summer is the time of year when the sun is farthest north from the equator. It is the longest day of the year, called solstice. (And, more significantly, it means school doors will be opening and thousands of schoolchildren will rush out for vacation.)

On the solstice, the sun sets at 8:07 p.m. and it doesn’t get dark until 9 p.m., which is a boon for night baseball and bad news for astronomers who star-gaze best with as little illumination as possible.

Summer lasts until Sept. 22--the autumnal equinox.

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“Summer solstice is a holiday in a lot of countries in Europe that are near or north of the Arctic Circle,” said John Sanford, president of the Orange County Astronomers Assn. “These are areas where the sun is always up and doesn’t set this time of year.”

Mosley said there are more subtle differences, such as the Earth’s tilt, that affect what day on which the solstice falls, especially over long periods of time. For example, if we looked at the dates for a summer solstice in the 7th century, it would have been June 18 or 19.

Otto Johnson, editor of the “1996 Information Please Almanac,” published in New York City, said he was pleased that his publication didn’t mislead its readers. The almanac got it right--summer came Thursday.

And something else of note: There are only 187 shopping days left till Christmas.

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(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)

The Summer Solstice

Summer began Thursday at precisely 7:24 p.m. with the summer solstice. The day of the summer solstice is the longest day of the year. It marks the time when the sun reaches its most northerly point. At this point, the North Pole is most directly tilted toward the sun and the Northern Hemisphere receives the most sunlight.

Source: World Book Encyclopedia, Griffith Park Observatory

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