From a New York Times story by Jonah E. Bromwich headlined “Here is a timeline of the events that led to the indictment”:

The investigation by the Manhattan district attorney’s office into Donald J. Trump’s involvement in hush-money payments to a porn star, which led to the indictment of the former president, has spanned nearly five years.

Here are some key moments:

AUG. 21, 2018
Michael D. Cohen says he arranged hush-money payments for the president, and the investigation begins.