Vernal Equinox in Thessaloniki, Greece
March 20, 2015
The length of day and night are approximately the same for all locations on the globe when the plane of Earth's Equator passes the center of the Sun -- the equinoxes. Though the Earth's axis is always tilted 23 1/2 degrees, on the date of the equinoxes the axis neither tilts away from the Sun nor towards it. These are the only times when the solar terminator, the line demarcating day and night, is actually perpendicular to the equator. This year's vernal equinox (for the Northern Hemisphere) is March 20, 2015, at 22:45 Universal Time (UT). Note that every location on the Earth experiences its own "local equinox" at local apparent noon on March 20.
On the date of last year's vernal equinox, also March 20, I captured the above montage of the Sun as it set above Thessaloniki, Greece. On the equinoxes, the Sun rises due east and sets due west. The street shown in the foreground (named Nikolaou Germanou) is oriented exactly east-west. The tower at right is a well know landmark of Thessaloniki called the White Tower.
Photo details: Image made with a full frame digital camera; 200mm lens at f/4; combination of filtered images with a Mylar filter in front of the lens; unfiltered exposures capture the foreground.