The late politician and war veteran McCain was not only Trump's Republican competitor but also served as a Senator from Arizona from 1987 until his death in August 2018.
The #JohnMcCainDay started trending on Twitter after Andy Lassner, the executive producer from popular day-time talk show "The Ellen DeGeneres Show" took to Twitter and launched the movement.
"Honoring an American hero today. Let's celebrate @realDonaldTrump's birthday today by having #JohnMcCainDay trend. I'm sure this would mean a lot to patriot like Donald Trump. #JohnMcCainDay," Lassner tweeted.
Twitteraties were seemingly quick and glad to join Lassner in the campaign.
"I don't know if I can trend #JohnMcCainDay but if you want I will post #JohnMcCainDay today to help because I think #JohnMcCainDay is better than celebrating the other thing. Oh Andy, I forgot... #JohnMcCainDay," Tony Posnanski, Mixed Martial Arts fighter replied to Lassner.
"@realDonaldTrump The only special thing about today is that's #HappyJohnMcCainDay," another user posted.
Lassner's tweet alone garnered 11,000 re-tweets, 26,000 likes and 23,000 comments.
The hashtag even topped the trending list on the micro-blogging platform.
Even though, Trump, who has been called 'master' of the platform by Twitter Co-founder, did not react to the hashtag, his supporters strongly dissed the trend.
"You are a producer who makes a good living and has a mega job yet you spend your time playing childish games on social media with a sitting President. Wow real manly of you Andy. Good job," Trump supporter and American-Canadian singer Kaya Jones tweeted.
Following the hate Lassner drew for his tweet, he took to the platform again to clear the air.
"Reading articles about #JohnMcCainDay. I want to set the record straight. I did not create the hashtag. People had tweeted it at me to get me to amplify it.
They're all the heroes. I'm so happy it took off. That said, I did create every other hashtag ever on Twitter," Lassner posted.
Trump, who is often trolled on Twitter for various reasons like spelling errors, has confessed that the platform for him is nothing more than just a "typewriter" to him.
( With inputs from IANS )