There have never been 100 days like this.

President Trump was sworn in for a second term in January intent on transforming America and its place in the world. From his first hours in office, he has relentlessly driven domestic, economic and foreign policy in risky new directions; taken a chain saw to the federal work force; challenged the authority of the courts; and sought to purge liberal influence from government, education and culture.

The result has been a chaotic blur of new initiatives; judicial, political and economic backlash; and neck-snapping reversals. It has tested the nation’s ability to process disruption — and of American democracy’s resilience in the face of a president whose views of his power have prompted warnings of creeping authoritarianism.

The consuming conflicts of one day regularly give way to wholly new ones with stunning rapidity: pardoning Jan. 6 rioters, stripping out-of-favor officials and former advisers of security details, proposing to turn Gaza into a resort town and Canada into a 51st state, blaming a plane crash on diversity initiatives, presiding over a contentious cabinet meeting with Elon Musk, installing his personal lawyers to run the Justice Department, firing inspectors general, closing down U.S.A.I.D., igniting a global trade war, berating Ukraine’s president in the Oval Office, deporting migrants without due process and edging toward a constitutional crisis by defying judges on multiple occasions.

If the 100-day mark is an opportunity to pause to reflect on what this presidency has meant so far — and what it could mean in its remaining 1,361 days — it offers one clear lesson. In this second time around, Mr. Trump is intent on using every hour to pursue an agenda shaped by a shifting mix of grievance, short-term political calculation, long-held belief and the experience of his first term.

Here’s a deeper look at how Mr. Trump has already made his mark.