LOS ANGELES (CBSLA.com) — Spring is ending, summertime is here – and the Griffith Observatory is ready to celebrate.

While many calendars identify the summer solstice as occurring on Friday, June 21, it actually occurs in Los Angeles at 10:04 p.m. on Thursday.

In most of the world, summer begins June 21, while the western U.S., Hawaii, Alaska, and selected Pacific Islands start their summer on June 20.

The summer solstice is the moment when the Earth’s orbital motion points the Earth’s North Pole most closely in the direction of the Sun. Earth’s axis of rotation is tilted 23.5 degrees from perpendicular to the plane of Earth’s orbit, and the tilt is the cause of the seasons.

Griffith Observatory will mark the occasion with experts Dr. Laura Danly and Dr. David Reitzel offering lectures at 12:55 this afternoon and 8:05 tonight as the Sun’s daily path follows its longest and highest arc across the sky for the year.

Click here to visit the Griffith Observatory website for more information.