Since the Naval Observatory depends on many guiding lights as the world turns, they have found the days of our lives moving faster.

"The {rotation of the} Earth has speeded up since a year ago," says Dennis McCarthy, an astronomer at the Naval Observatory. "We can only measure this using astronomical observations."

The faster rotation means that all observatories must, sooner or later, compensate for the decrease in time. By adding a leap second to their precise atomic clocks, they catch up to the speed of the Earth's spin.

Decisions on whether to insert a leap second come from the Bureau International de l'Heure (International Bureau of Time) in Paris. The Naval Observatory expected a leap second this month, but the Bureau decided not to add one now. The last leap second was inserted 2 1/2 years ago, while it is normal to add one every 12 to 18 months.

McCarthy explains that reasons for the rotational increases or decreases vary. Surface wind speeds can hamper the Earth's spin, as can shifts in this planet's mass.

McCarthy now expects the leap second to be added in December but, while you wait to turn time forward, you can set your watch to the Naval Observatory's Master Clock by calling 653-1800.

In matters of another world:

Saturn starts the summer shining bright. You can see this planet with your naked eye, but with a small telescope you can even see its rings clearly. If you gaze about 10 p.m., face the southeast, look about halfway up the sky and you will find Saturn shining brightly at 0.0 magnitude (very bright). Saturn will generally rest under the constellation Ophiuchus and to the left of the star Antares.

The Sun reaches its highest point in our sky June 21, making that day the year's longest. It means the sun is at its solstice and it marks the first day of summer in the Northern Hemisphere. Summer officially starts at 6:11 p.m. EDT. From there out, by the way, the hours of daylight start getting shorter.

For the young and the restless:

Saturday -- Touch a moonrock or tour a mock of the space shuttle at the Goddard Space Flight Center. Goddard is helping to celebrate Greenbelt's 50th anniversary by sponsoring an open house 10 a.m.-5 p.m. The center also will feature the Roosevelt High School String Quartet at noon and 1 p.m. A shuttle bus will run between the celebration in Greenbelt and Goddard. Admission is free.

Saturday -- Jan Herman, historian of the Old Naval Observatory, discusses the observatory's 26-inch refracting telescope. It was the world's largest telescope -- in 1873. The 9:30 a.m. lecture at the Einstein Planetarium, National Air & Space Museum, is free.

Sunday and June 21 -- Launch a model rocket, or just watch them roar off, at the Goddard Space Flight Center. 1 p.m. Free.

June 13 and 14 -- "Flying Machines" a NASA film on aviation history and "4 Rms-Earth View" a documentary about Skylab, will be shown at the Goddard Visitors Center. 1 p.m. Free.

June 17 -- The sky may look calm, but the stars experience a dramatic life-cycle that lasts a few billion years. Harry Shipman, a physics professor from the University of Delaware, will explain in his lecture, "Star Formation and Stellar Demise," at the Einstein Planetarium, Air & Space Museum, 7:30 p.m. Free.