A new chapter in global history — the pandemic era — came crashing into existence four years ago Monday.

The big picture: It's pretty rare to be able to point to a single day that transformed the whole world. But March 11, 2020, is one of those days.

March 11 was, formally, the day the World Health Organization declared a pandemic. It was also the beginning of pandemic life as we know it colloquially.

• March 11 was the day Tom Hanks announced he had contracted the virus — a jarring moment for Americans who had spent the past few weeks not quite sure how scared they should be.
• It was the day the NBA canceled the rest of its season. Pretty much every other event that brought together large numbers of people followed suit shortly thereafter.
• It was the day then-President Trump imposed a new travel ban from Europe. Even domestic air travel quickly began to crater, bottoming out later in the month.
• New York City forced all bars and restaurants to close a few days later, though many of them already had.

In part because of catastrophic testing failures, there were only 1,135 confirmed COVID cases in the U.S. on March 11, 2020, and 38 deaths. COVID has now killed more than 7 million people worldwide, and more than 1 million people in the U.S.

• The pandemic destroyed entire industries, birthed others, and transformed the rest.
• It briefly brought Americans together in a moment of shared sacrifice that might have seemed impossible, only to then rip new holes in the social and political fabric, some of which have only gotten bigger.
• It exposed and exacerbated deep inequalities in health care, the labor force and the broader economy. For the most part, they persist.
• It ushered in astounding scientific advances — extraordinarily effective vaccines, developed in record time. And yet the anti-vaccine movement is now as mainstream as it's ever been.