presidential primary debates starting in June 2019
(Image removed from quote.)
That's not historically too bad really. While I'm at it...earliest set of announcement dates for a few candidates in the past few cycles:
May 2002 - Howard Dean
December 2002 - John Kerry
January 2003 - John Edwards, Dick Gephardt, Al Sharpton, Joe Lieberman
May 3, 2003 - First Dem Debate
March 2006 - Joe Biden
April 2006 - Mike Gravel
May 2006 - Chris Dodd
November 2006 - Johm McCain, Rudy Guiliani, Tommy Thompson, Tom Vilsack
December 2006 - Evan Bayh. Sam Brownback, Dennis Kucinich, John Edwards, Jim Gilmore (Also Evan Bayh withdraws 15 days after announcing)
January 2007 - Mitt Romney, Ron Paul, Tom Tancredo, Barack Obama, Hillary Clinton, Bill Richardson, Duncan Hunter, Mike Huckabee
April 26, 2007 - First Dem Debate
May 3, 2007 - First GOP Debate
January 2011 - Herman Cain
March 2011 - Newt Gingrich, Buddy Roemer, Tim Pawlenty
April 2011 - Mitt Romney, Rick Santorum, Gary Johnson, Ron Paul
May 2011 - Jon Huntsman
May 5, 2011 - First GOP Debate featuring Cain, Johnson, Pawlenty, Paul and Santorum

June 13, 2011 - First GOP Debate with Bachmann, Romney and Gingrich
November 2014 - Jim Webb
December 2014 - Jeb!
January 2015 - Chris Christie, Martin O'Malley, Lindsey Graham
February 2015 - George Pataki
March 2015 - Ben Carson, Donald Trump, Ted Cruz
April 2015 - Rand Paul, Lincoln Chaffee, Rick Santorum, Hillary Clinton, Marco Rubio, Bernie Sanders
August 4, 2015 - First GOP Debate
October 13, 2015 - First Dem Debate
edit: I used dates of forming "exploratory committees" not the often much later media "announcements" as I can't recall any major candidate forming one and then not actually entering the race...and some of them the candidates were running around for six months, and even debating, before "announcing"
also Joe Biden announced twice during the 2008 cycle, along with announcing the forming of an exploratory committee...the date is actually his first announcement, then in 2007 he forms a committee then quickly announces again after Obama, Hillary, etc. all announce...good ol Diamond Joe