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CNN  — 

Wednesday marks Joe Biden’s first day as US president, but you’re going to hear a lot about his first 100 days as he takes the reins, particularly when it comes to Covid.

That gets us to April 30.

The list of what Biden hopes to do between now and then, in part:

He’s also got a slate of Day One executive orders meant to undo what President Donald Trump has wrought over the past four years, including:

Here’s a full list.

That will be followed by executive orders on Thursday and Friday regarding Covid and economic support for Americans.

Biden’s also pledged the most diverse Cabinet in history and said it would look like America. Here’s an interactive that shows how he did.

Biden will be tackling this enormous to-do list as Congress navigates the impeachment trial of his predecessor (which may or may not feature Chief Justice John Roberts).

It’s a lot to get done in 100 days, far less than an NBA season, particularly when you pair it with the fact that the Senate has not confirmed or even scheduled a vote on a single one of Biden’s Cabinet nominees. The first group had their initial hearings on Tuesday.

What’s the rush?

Nobody needs deadlines more than lawmakers, although Congress rarely gets much of anything done before the last possible moment. “As a veteran of national politics, Biden understands that the most valuable commodity for any new President is time,” writes presidential historian Julian Zelizer, casting back to LBJ’s effort to make the most of his time before politics took over.

For LBJ, that meant 1965 and half of 1966 before he expected to lose seats in Congress during the midterm elections.

For Biden, in this hyperpartisan era, it almost surely means much less time. He is deeply aware of how Republicans played obstructionist during the entire Barack Obama administration and refused to materially buy into any major piece of legislation, including stimulus, Obamacare and Wall Street revisions, although there were exceptions on stimulus and Wall Street.

Obama started his term with a filibuster-proof 60-vote majority in the Senate. Biden starts his with 50.

Some unexpected thing will happen. Obama lost that key 60th seat when Teddy Kennedy died and a Republican won the special election. Obamacare has been set during the decade since as the flawed law that had already passed the Senate because it’s impossible to fix things in frozen Washington.

The closer analogy for Biden now is 2001, when Republicans turned off Sen. Jim Jeffords, who was unhappy that George W. Bush and his fellow Republicans in Congress were giving short shrift to funding for special education.

Jeffords left the GOP in March, well within Bush’s first 100 days, handing control of the Senate to Democrats and foiling Bush’s first-term plans.

That’s the difficulty of leading. Biden will have to keep everyone who’s in the Democratic tent on his team and get help from a non-insubstantial group of Republicans, which will require momentum and urgency.

What’s Biden’s overarching goal?

Zelizer compares Biden’s 100-day plan with those of other presidents and sees a key difference:

Unlike some other famous first 100 days, like FDR’s in 1933, Biden’s plan primarily aims to reverse the direction of policy under his predecessor and stabilize society from the pandemic rather than set out on a fundamentally new path that remakes public policy. Nonetheless, given the circumstances, the plan is extremely ambitious.