Old man in a hurry.

Joseph R. Biden Jr. is 78 years old. He is the oldest person to occupy the White House. And as he approaches the traditional hundred-day presidential evaluation marker this week, he has set a stunning, breathless pace.

He has won approval of a stimulus bill, has proposed an infrastructure offensive and has placed a tax bill on the American agenda. He has announced the withdrawal of American troops from Afghanistan, challenged Russia on cyber interference, engaged China in a sobering trade reckoning, taken steps to return to the Iran nuclear agreement, and set out goals to battle climate change.

Handfuls of younger presidents treaded more carefully and more modestly in their hundred-day periods, which, since Franklin Delano Roosevelt’s torrid pace of 15 major pieces of legislation, has become the customary period for grading a newly inaugurated president. The phrase Hundred Days is derived from the time between Napoleon’s 1815 return to Paris from Elba exile and his defeat at Waterloo.

Maybe Biden is in a rush because he is old.

“When people are older, their perspective narrows, and when they are older they truly often are wiser and they have perspective and clarity,” said Janet Taylor, a community psychiatrist in Sarasota, Florida, and a consultant with AARP. “They accept that they have more time behind them than in front of them. Biden in a hurry? Sure. Focused on what’s most important and determined to get that done? Definitely.”

As the country ages — the Urban Institute estimates that the number of Americans 65 and older will more than double over the next four decades — this may become a more significant political and cultural phenomenon. Consider the character of the country in 2040, with 80 million American senior citizens.

Even now, Biden is challenging the old paradigm of the young man in a hurry, a phrase that might be traced to an 1848 French play titled “Un jeune homme presse.”

Modern Americans are familiar with two figures who lived that young-man genre, both shaped by the early deaths of their fathers, both in a hurry to leave a mark because they knew of the fragility of life and the threat of early demise.

The first was Mickey Mantle, whose father, Elven Clark “Mutt” Mantle, died in 1952 at age 40. The Yankee slugger lived to be 63 but conducted his life in the supersonic speed that first was achieved by Air Force Maj. Charles E. Yeager on a Bell X-1 rocket-powered research plane, in the year the future baseball star turned 16.

“He lived every day as though that day would be his last,” said Peter Golenbock, author of “7: The Mickey Mantle Novel.” “He lived hard. He was a drinker, he was a womanizer and he never wanted to feel cheated. He was sure he would die at 40.”

The other was Bill Clinton, whose father, the heavy equipment salesman William Jefferson Blythe Jr., died at age 28, just before the future president was born, drowning after a tire blew out as he was driving in Missouri.

“Bill was always in a hurry, for sure,” said Paul David Leopoulos, whose friendship with the 42nd president dates to when the two of them were 8 years old.

“He felt grateful for every year he lived beyond how long his father lived,” said Carolyn Staley, who grew up next door to the young Clinton. “And for that reason, he always needed to seize the day and didn’t know how much time he had. He felt he was living on a short string.”

Even so, Clinton’s first hundred days were unimpressive.

The conservative Heritage Foundation dismissed his record as “a sorry scorecard.” Even liberals were disappointed. The new president was swept into office on a gale of optimism but swiftly became bogged down in disputes over gays in the military and undocumented domestic workers in the homes of Cabinet appointees. His brave plans for a national childhood vaccine program, a college-for-all scheme and a campaign-finance overhaul were abandoned, watered down and postponed, respectively.

Alistair Cooke, the shrewd British observer of all things American, told his BBC listeners: “No need to recite the distressingly long list of campaign promises gone back on, bold programs discreetly modified, initiatives revised and withdrawn, enough to remind you first of the sound defeat he took from Congress with some of his own party having the gall to join in the massacre of his $16 million economic stimulus program.”

Still, Clinton persevered, and though beleaguered by personal scandal, left office with America at peace and in prosperity, and with high approval ratings. His presidency suggests the opening theme may be less important than the coda.

Biden’s determination to open with a brisk scherzo — and, so far, to avoid the kind of fiasco the 43-year-old John F. Kennedy endured with the botched Bay of Pigs episode on Day 85 of his presidency — may be because he has known tragic loss, and the suddenness with which it sometimes occurs; his wife and 1-year-old daughter perished in an automobile accident just after his election to the Senate in 1972, and his son, Beau Biden, died of brain cancer. He understands the smudge in the human story between life and death. When he pops into Janssen’s Market, his favored grocery store in Wilmington, Delaware, he may pause and choose the bright-yellow bananas rather than the green ones.

“Maybe through his Catholic faith or through his tragedies, he has made the shift from ‘adulthood’ to ‘elderhood,’” said Richard Leider, a prolific author on “aging with purpose” who also has worked with AARP. “There isn’t much ritual around that shift, but Biden seems to see a larger reason for being beyond his political will or ego. He is answering an existential ‘why’ question: Why am I doing this?”

The phrase “old man in a hurry” has not always been employed in a positive light. It first was used by Lord Randolph Churchill in 1886, when he was 37 years old and impatient with William Ewart Gladstone’s drive for Irish home rule. He questioned the British prime minister’s motives for calling an election, saying, “Why? For this reason and no other: to gratify the ambition of an old man in a hurry.”

You might hear a history-minded Republican quoting that Randolph Churchill speech before long.