Astronomy: today at sunset, NYC turns into Stonehenge

An unusual sunset in Manhattan. Snip from NASA "astronomy pic of the day":

Today, if it is clear,
Manhattan will flood dramatically with
sunlight just as the Sun sets precisely on the
centerline of every street.

Usually, the tall buildings that line the gridded streets of
New York City's tallest borough will hide the setting Sun.

This effect makes Manhattan

a type of modern
Stonehenge,
although only aligned to about 30
degrees east of north.

Were Manhattan's road grid perfectly aligned to east and west,
today's effect would occur on the
Vernal and
Autumnal Equinox,
March 21 and September 21, the only two days that the

Sun rises and sets due east and west.

If today's sunset is hidden by clouds
do not despair
the same thing happens every May 28 and July 12.

Link. Image: 2001, Neil deGrasse Tyson. (thanks, Andrew, via ninjaslice)