US President Donald Trump has congratulated Princess Eugenie on the royal wedding in a tweet that left some social media users baffled.

Mr Trump tweeted his message to the Princess of York and new husband Jack Brooksbank on Sunday, but somehow got his days mixed up.

In a bizarre post, he praised the Princess on coming out as a “winner” after “going through so much”.

The timing of the American leader’s tweet suggested that the wedding at Windsor Castle took place on Saturday, when it actually happened on Friday, The Sun reported.

Social media users were quick to point out the President’s error in replies to his pronouncement.

Meanwhile, people were also trying to work out what Princess Eugenie had “been through” that Mr Trump referred to in his baffling message.

Many believe that it’s a reference to the scoliosis that she had treated as a child.

The Queen’s granddaughter was diagnosed with the condition aged 12, in which the spine twists and curves to the side and requires correcting rods to be placed into the body surgically to straighten it out.

TRUMP CASTS DOUBTS ON DEFENCE SECRETARY JAMES MATTIS
Meanwhile, Mr Trump has suggested that Defence Secretary James Mattis may be among the next high-level Cabinet officials to step down, calling the general a “good guy” but “sort of a Democrat.”

The New York Post reported that while Mr Trump had a “very good relationship” with his defence chief, the president said “it could be” that Mr Mattis will depart the administration, although the general hasn’t told him so.

“I think he’s sort of a Democrat, if you want to know the truth,” Mr Trump told 60 Minutes in an interview to air on Sunday night in the US. “But General Mattis is a good guy. We get along very well. He may leave. I mean, at some point, everybody leaves. Everybody. People leave. That’s Washington.”

The comments come after the announced departure of United Nations Ambassador Nikki Haley and the expected shake-up at Attorney-General Jeff Sessions’ Justice Department after the midterm elections.

Mr Trump’s White House has already set a staff turnover rate of 37 per cent through June 30, the Associated Press reported, and set new records for attrition.

Mr Trump dismissed reports that his White House is in chaos as just “wrong.”

He said he’s entitled to staff shake-ups and has “phenomenal” people on standby to come work for his administration.

“I have some people that I’m not thrilled with,” MR Trump said. “And I have other people that I’m beyond thrilled with.”