Thirty-eight years ago today, Jimmy Carter hosted a well-known houseguest at 1600 Pennsylvania Ave. -- and made him sing for his supper. On a lovely late-summer evening, Willie Nelson performed on the South Lawn, a set that included a duet with Rosalynn Carter.

After bidding the president good night, Willie retired to his own room. He was restless, however, and after the First Family was safely abed the great country singer went to the White House roof where he took in the sights of the capital city and fired up a fat boy.

Nelson revealed his midnight toking in his autobiography -- he called his joint “a big fat Austin torpedo" -- although it wasn’t a revelation that surprised anyone. Marijuana is in the process of being decriminalized in the U.S. these days, but that wasn’t the case in 1980. Willie Nelson was a man ahead of his time: He’s had as many marijuana arrests as wives (four), and has served on the board of directors of NORML, the National Organization for the Reform of Marijuana Laws.

The president wasn’t on the White House roof smoking weed with Willie on September 13, 1980, which is just as well: More worldly souls than Jimmy Carter have tried, and failed , to hang with the singer in that pursuit. On the other hand, it might have helped Carter relax. It was a trying time in his presidency. The U.S. economy remained in the dumpster, the Iranian hostage crisis showed no signs of abating, and it had finally dawned on Carter that Ronald Reagan, his general election opponent, was one tough customer.

A longtime dry fly fisherman, Carter found solace by tying flies while listening to Willie Nelson’s records and reading the Bible at night. But on this evening 38 years ago, Carter derived pleasure from hearing his old pal team up with the first lady on a spirited rendition of “ Up Against the Wall, Redneck Mother. ”

Jimmy Carter will turn 94 in a couple of weeks. Willie Nelson is 85. Neither man has retired. Six years ago, Willie was performing at Atlanta’s Chastain Park amphitheater when he invited Jimmy and Rosalynn Carter on stage to join him in “Amazing Grace.”

Carter, not exactly known for letting his hair down as president, even donned Willie’s trademark red bandana for the occasion. Times (and technology) being what they are, someone in the audience recorded it . It’s not great filmmaking, or even great music anymore, but what took place on that Georgia night was a pretty good definition of aging gracefully.

They are still at it, both guys, and they aren’t sitting out the 2018 election season, either.

At his annual July 4 picnic and concert this year, Willie invited Texas senatorial candidate Beto O’Rourke onstage to join him in closing out his set. O’Rourke had brought his guitar for the occasion, just in case, and joined the band in playing “Will the Circle Be Unbroken?”

In two weeks’ time, Willie is scheduled to be one of the headliners for an O’Rourke rally in Austin -- the first time in the singer’s long career, according to Rolling Stone magazine , that he’s done a public performance for a political candidate.

Meanwhile, Jimmy Carter is looking even farther into the future -- to the next presidential election. Carter tempers his criticisms of Donald Trump by warning Democrats that this isn’t the time for them to veer too wildly to the left. “I don’t think any Democrat is going to vote against a Democratic nominee,” he said earlier this week at The Carter Center, the site of his presidential library in Atlanta. “Independents need to know they can invest their vote in the Democratic Party in 2020.”