Google confirmed on March 13, 2019 that "this week, we released a broad core algorithm update, as we do several times per year", and Danny Sullivan confirmed the rollout had started on March 12. Google did not announce a completion date; formal rollout-complete announcements were not yet standard practice in 2019.
The naming is what made this update historic. Brett Tabke, owner of WebmasterWorld and Pubcon, dubbed it "Florida 2" because a Pubcon Florida conference was under way, a nod to the original 2003 Florida update, but Search Engine Land stressed the two were unrelated algorithms. On March 15 Google stepped in with an official name: "Our name for this update is 'March 2019 Core Update.' We think this helps avoid confusion; it tells you the type of update it was and when it happened." Every core update since has followed that month-and-year structure.
Google's recovery guidance was already the familiar one: "there's no 'fix' for pages that may perform less well other than to remain focused on building great content." If a site moved during this window, the standing advice in Google's core updates documentation applies, and our recovery guide covers the sequence.