Automatic Data Processing President and CEO Carlos Rodriguez and activist investor Bill Ackman have resolved their differences since Ackman lost a proxy fight against the payroll giant, Rodriguez said Wednesday.

"It's all water under the bridge," the CEO told CNBC in an interview with "Mad Money" host Jim Cramer. "We listened very carefully to what Bill had to say. In fact, I've been in touch with him, so we have, I think, what I would call a collegial and professional relationship."

In an August 2017 interview with CNBC, Rodriguez slammed Ackman, saying the Pershing Square chief reminded him of a "spoiled brat." In November, Ackman slammed back, calling ADP "very inefficient."

The battle ostensibly came to an end when Ackman lost his bid for a seat on ADP's board, though he remained a shareholder.

But on Wednesday, Rodriguez brushed the contentious back-and-forth under the rug.

"I don't think there's any disagreement about the potential that ADP has. It's really about pace," the CEO said. "You can always move a little bit faster, so there's nothing wrong with someone pushing us to move quicker and have a little more of a sense of urgency."

For Rodriguez, the results speak for themselves. Just this morning, ADP delivered a strong earnings beat on the top and bottom lines and raised guidance due to a number of economic tailwinds.

"As a matter of fact, [Ackman] did call to congratulate me" on winning the proxy fight in November, Rodriguez told Cramer. "I think it's a good, productive relationship now."

Rodriguez also said that the current economic environment is "practically perfect" for ADP, the country's largest payroll processor.

The company's high effective tax rate will be reduced by corporate tax cuts, raising the potential for a dividend boost for ADP. In addition, better economic activity, slightly higher inflation and rising interest rates are all boons for the administrative colossus, the CEO said.

Rodriguez said that ADP's data is also signaling wage inflation, another positive economic catalyst.

But the CEO was focused on a broader trend that is changing what many consider to be the fabric of the American workforce.

"The nature of the workforce is changing and gig workers are one of the factors," Rodriguez said. "The most popular image that people have of that is Uber and people kind of working on the side, but it's really across the whole economy. There's approximately 35 million people who work as independent contractors or get a 1099, and ... they need help in terms of compliance, they need help with managing their finances, and the employers who use them as independent contractors need that help as well. So it opens up a whole new market for us in addition to the W-2 employees, which are our traditional source of business."

Correction: This story has been updated to reflect that Rodriguez said Ackman called to congratulate him on winning the proxy fight.