One day after Swedish climate change activist Greta Thunberg was announced as Time magazine's Person of the Year, President Donald Trump mocked the 16-year-old on Twitter, telling her to "work on her Anger Management problem."

"So ridiculous," Trump said in a tweet on Thursday morning. "Greta must work on her Anger Management problem, then go to a good old fashioned movie with a friend! Chill Greta, Chill!"

His tweet was in response to actor and author Roma Downey congratulating Thunberg on the Time honor. Downey is married to Mark Burnett, creator and producer of The Apprentice, which Trump hosted.

Trump's tweet was poorly received. Many criticized him for singling out the teenager once again and suggested he was jealous that he wasn't picked as Person of the Year.

Others pointed to first lady Melania Trump's anti-bullying Be Best campaign, and her comments earlier this month chastising legal scholar Pamela Karlan, who made a pun about Barron Trump during the Trump impeachment hearings.

"A minor child deserves privacy and should be kept out of politics," the first lady had tweeted. "Pamela Karlan, you should be ashamed of your very angry and obviously biased public pandering, and using a child to do it."

"@FLOTUS what was that you were saying last week about attacking minors?" one Twitter user asked after Trump's Thursday tweet.

Trump's affinity for Time's Person of the Year precedes his time in politics. A fake Time cover featuring him as Person of the Year was found at his golf clubs. He ultimately received the honor for real in 2016.

But he's also complained about not being selected for the honor several times this decade, and in 2017 claimed he turned it down after the magazine told him he "was PROBABLY going to be named 'Man (Person) of the Year,' like last year" with conditions. The publication denied his claim and honored "The Silence Breakers," who were the women who spoke out against sexual harassment as part of the #MeToo movement.

Thunberg, who has been the target of angry Trump tweets in the past, did not respond to the president, but she changed her Twitter bio shortly after.

Her quiet but classy move was widely praised on Twitter.

"Greta Thunberg is handling being bullied by the President of the United States much better than I would be," one user tweeted. "I’m genuinely proud of her."