Twice a year, Manhattanites are treated with a spectacular sunset. On the dates of roughly May 29th and July 12th (see below for exact dates of the current year), New Yorkers can stand in the middle of any of the East-West crossing numbered streets on the grid of Manhattan -- with a clear view to the Hudson river -- and find that their city is perfectly aligned with the setting Sun.
When the commisioners plan of 1811 was put into place declaring Manhattan would have 90 degree angle streets, a bullseye was created for the Sun to hit. Many other gridded cities may have a similar bullseye, however Manhattan has the advantage of being flanked by a river on the Eastern and Western sides. Additionally, the view toward sunset stares at cities in New Jeresy which - luckily but maybe not permanently -- have relatively flat skylines. Regardless, I encourage you to head outside at Sunset wherever you live and see what kind of "henge" might be waiting for your city.
Manhattanhenge is a lesson in Astronomy 101: a reminder that we live on a rock that is spinning at a tilt as it swiftly moves through space in orbit around the Sun. From day to day, you will find that the Sun sets at a different position. The video below should give you a nice visual of how this happens. I've overlaid the grid of Manhattan with the line of sight toward the setting (orange) or rising (yellow) Sun on various days of the year. You can think of this as if you were standing in the middle of say 79th street (up high so you had a clear view to the horizon) and pointing at exactly where you saw the Sun at the moment it set. Follow that line from your arm out all the way to the horizon and that's the angle of the colored line. As you can see, the Sun marches it's way North and South of the grid from solstice to solstice. On Manhattanhenge dates, it is perfectly between your favorite skyscrapers.
For Manhattanhenge 2019 I've calculated the following dates and times. A slight inside tip is that the day before (after) the May (June) dates will also have a pretty spectacular sunset close to the grid.
May 29th 8:12 (and 30s) pm (Half Sun) July 13th 8:21pm (Half Sun)
May 30th 8:12pm (Full Sun) July 12th 8:20pm (Full Sun)
Another tip is that I like to call the May Manhattanhenge the "Welcome the Sun to the grid!" event. Everyday after the May event, the Sun will set a little further South from the grid. But that means it will cross between your buildings a little higher every day until the summer solstice. Then it reverses its position and backs its way out of the grid, setting north of the city through the end of the Summer, fall, winter, and spring.