Manhattanhenge happens when the sun aligned with Manhattan’s street grid. The most popular spots to watch the Manhattanhenge are 42nd Street with its flashing signs, as well as 57th, 34th, 23rd, and 14th Streets.
For the year 2020, you can expect to see the Manhattanhenge on:
Friday, May 29, 8:13 p.m.
Saturday, May 30, 8:12 p.m.
Saturday, July 11, 8:20 p.m. 
Sunday, July 12, 8:21 p.m. 
Here is my tip for you: photograph it a day before or after. You’ll have almost the same view minus the crowd. 

Manhattanhenge as seen from 42nd street

Manhattanhenge as seen from 14th street