PANAMA CITY BEACH — Wayback Burgers will celebrate Friday, June 20 — the first day of astronomical summer/summer solstice/longest day of the year — with its annual Free Shake Day. Guests can enjoy a free 12-ounce vanilla milkshake, no purchase necessary, at participating locations nationwide.

During the summer solstice, the Sun rises over the Tropic of Cancer (23° 26' latitude) in the Northern Hemisphere. In contrast, in the Southern Hemisphere, the Sun rises over the Tropic of Capricorn (−23° 26' latitude). This year in the northern hemisphere, summer officially starts on June 20 at 10:42 p.m., when the summer solstice happens.