Like many companies these days, Bloomberg requires employees to carry badges and swipe into the office.

Unlike most, the company displays the time stamps internally on employee bio pages and emails so you can see when colleagues badge in and out.

The practice goes back to the 1990s and explains a lot about how Mike Bloomberg manages.

Mike saw it as useful information, but he also knew that displaying times would encourage people to arrive early and stay late.

In 2008, while Mike was serving as mayor of New York City, Dan Doctoroff became CEO of Bloomberg LP.

At some point, some employees complained to Dan that the time stamps made them uncomfortable. They didn’t think everyone needed to know when they came and went.

Dan removed the time stamps. He left intact an indicator that signaled if the person was in the office and online.

It was a big enough deal that the New York Post wrote a story about it.

Mike returned in 2014 and noticed the missing time stamps. He told the programmers to put them back.

Time stamps were, evidently, a feature not a bug.

I was in a meeting with Mike in which he explained his thinking.

He knew the people who came in early viewed time stamps as a kind of merit badge. He wanted to encourage those people. Mike typically badged in by 7 a.m.

I never saw anyone punished for coming in late. But the time stamps contributed to a longer-working culture.

Mike recounts in his book that he succeeded at his first job at Salomon Brothers in part because he got in early and left late, providing him an opportunity to connect with top executives like Billy Salomon and John Gutfreund.

Some companies mandate start times. They effectively rely on rules to set standards.

Mike was more inclined to move the social furniture to guide behavior.

Time stamps at Bloomberg are an example of establishing standards without setting a hard rule.

In the three decades I worked at Bloomberg, I was never given a time to start the day.

It wasn’t necessary to be told, of course.

Everyone could see the time stamps and figure it out.

(Part of a series of lessons I learned from three decades at Bloomberg LP.)