The streets of New York, on July 13th

As it happens, then, Manhattan's mathematically rational street grid is actually rotated 29º off the north-south axis – and this angle has interesting astronomical side-effects.

In other words, because of the off-center orientation of Manhattan's street grid, you can only see the setting sun "down the middle of any crosstown street" on two specific days of the year: May 28 and July 13.

July 13 is, of course, next week – so watch out for it.

Manhattan is a solar instrument that only works twice.So, because of historical decisions made about the logic and purpose of urban planning – and because of the declination of the Earth's poles – the streets of Manhattan are aligned with the setting sun only two times a year.

Via http://bldgblog.blogspot.com/