Kim's birthday is believed to be January 8, though his secretive regime has never confirmed the date.
The US government lists Kim's birth year as 1984, making him 40 years old this year.
The birth dates of Kim's father and grandfather, who preceded him as rulers, are national holidays in the authoritarian state.
Kim Jong-un's presumed birth date, meanwhile, has always passed quietly without mention in media or on the country's calendars.
The closest North Korea has come to confirming the date came in January 2020 after authorities acknowledged Kim had received birthday greetings from then-US president Donald Trump, though they did not mention the exact date.
This year, state news agency KCNA on Monday showed Kim visiting a chicken farm with his daughter and senior officials.
South Korea's intelligence agency said this month it believes the daughter, known as Ju-ae, may be a likely successor.
Kim's government is heavily sanctioned over the country's nuclear weapons and ballistic missile programs, as well as human rights abuses.
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