Sundial on Parnidis Dune, Curonian Spit, in Lithuania

It's time for spring

This 40-foot sundial stands atop the Parnidis Dune, one of the scenic highlights of Curonian Spit, a UNESCO World Heritage Site shared by Lithuania and Russia. Built in 1995, the sundial was damaged by a hurricane a few years later and rebuilt in 2011. It accurately tells time by creating shadows on the steps, with notches for hours and half hours, as well as months, equinoxes, and solstices.

March 20 marks the spring (or vernal) equinox in the Northern Hemisphere, meaning that for the next six months daylight hours will outlast nighttime darkness. When it's winter in the Northern Hemisphere, those of us above the equator are tilted away from the sun, giving us shorter days and longer nights. In summer, we're tilted toward the sun, but the equinox is right in between. It's the moment during Earth's annual revolution around the sun when its axis is neither tilting away nor tilting toward the sun, giving everyone on the planet an equal split of day and night. This phenomenon happens twice a year—in March and again in September. In the Southern Hemisphere, everything's flipped. There, it's the autumnal equinox today — and, yes, winter is coming.