By James Sergent, Ramon Padilla and George Petras, USA TODAY

Forget their policies. Age is one of the biggest differences in the 2020 presidential race.

More than a generation separates the oldest and youngest candidates on the Democratic side. South Bend, Ind., Mayor Pete Buttigieg and Rep. Tulsi Gabbard are 40 years younger than Sen. Bernie Sanders and 39 years younger than former Vice President Joe Biden.

On the Republican side, President Donald Trump, the oldest first-term president, and former Massachusetts Gov. William Weld would also be in their mid-70s on Inauguration Day.

Of course, age has little to do with a president’s success. John F. Kennedy (the youngest president) and Ronald Reagan (the oldest) rank among the top 15 of U.S. presidents, according to Siena College's annual poll.

Reagan, in his early 70s, famously deflected a question about his age during his 1984 re-election campaign against 56-year-old Walter Mondale: "I will not make age an issue of this campaign. I am not going to exploit, for political purposes, my opponent's youth and inexperience."

Still, age is a lens that colors our view of the world. Buttigieg and Gabbard were about 7 when the modern internet was born; Biden and Sanders were born during World War II and lived through a handful of other wars and conflicts.

Our timeline gives you a sense of just how wide the gap is between the Democratic and Republican candidates.