Democratic socialist Zohran Mamdani was sworn in as New York City mayor, making history as New Yorks first Muslim, first South Asian and first African-born mayor, and at age 34, the citys youngest mayor in generations. The historic inauguration marks a significant shift in American urban politics.
In international news, Denmark announced it will send a substantial number of troops to Greenland in response to threats from United States president Donald Trump, escalating tensions over Arctic sovereignty.
A high court in Seoul, South Korea, sentenced former president Yoon Suk Yeol to five years in prison for obstructing justice and excluding cabinet members during his 2024 martial law declaration, while acquitting him of document forgery.
Economic milestones were also reached: Bulgaria adopted the euro, replacing the lev and becoming the 21st member of the eurozone. Steel and aluminium exporters to the EU started paying for the CO2 emissions linked to their production as of January 1, 2026.
Argentina recorded a 31.5% annual inflation rate in December, the lowest end-year level since 2017, signaling potential economic stabilization in the South American nation.
In demographic news, Chinas birth rate fell to 5.6 per 1,000 people last year, the lowest since records began in 1949, reflecting a broader demographic decline across East Asia that economists warn could have long-term economic implications.
Natural phenomena also made headlines as the Sun released the largest solar particle event towards Earth since the 2003 Halloween solar storms, prompting heightened monitoring of communications systems worldwide.