Joe Biden checked his watch 15 minute before his final debate with President Donald Trump ended on Thursday night, Oct. 22, prompting doubts on impatience or weariness of the 77 years-old Democratic presidential candidate.

When moderator Kristen Welker of NBC was raising a question about climate change for the two candidates, Biden shifted his shirt sleeve up and looked at his wrist watch for a moment.

Biden repeats a mistake made by former President George H.W. Bush who checked his own watch during a town hall debate with former President Bill Clinton and Texas billionaire Ross Perot in 1992.

That move is often considered signifying that the candidate is tired, impatient, or bored of the debate, or even seen as disrespect for the moderator’s question.

President Trump’s supporters took over Twitter to mock Biden over his move, calling it “nap time” and “time to take his meds.”

During the debate on climate change, President Trump touted that his administration has created the cleanest water, the cleanest air, and the lowest number in carbon emissions in 35 years.

President Trump argued that he decided to withdraw the United States out of the Paris climate accord because it was a very unfair deal, which would have cost the country trillions of dollars and hurt businesses.

Biden said that climate change and global warming are existential threats to humanity.

“We have a moral obligation to deal with it. And we are told by all the leading scientists in the world, we don’t have much time. We are going to pass the point of no return in eight to 10 years,” Biden said, adding that four more years of the Trump administration would eliminate all the regulations that were put in to clean up the climate and limit emissions.

“I was able to get the environmental organizations as well as labor, people worried about jobs, to support my climate plan,” Biden added.

But the president said that Biden’s plan to tackle climate change and invest in green industries was developed by Rep. Alexandria Ocasio-Cortez (D-N.Y.).

Biden finally replied, “I don’t know where he comes from.”