The presidency of Donald Trump began at noon EST (17:00 UTC) on January 20, 2017, when Donald Trump was inaugurated as the 45th president of the United States, succeeding Barack Obama. Trump rolled back numerous environmental protections, as well as reduced enforcement of existing regulations. He ended the Clean Power Plan, withdrew from the Paris Agreement on climate change mitigation, and urged for subsidies to increase fossil fuel production, calling man-made climate change a hoax. Trump failed in his efforts to repeal the Affordable Care Act (ACA), but took numerous actions that hindered its functioning and sought to have the courts rule it unconstitutional. Six Trump campaign advisers and staff were indicted and five pled guilty to criminal charges. None of the bills passed by Trump are considered to be 'major bills'—based on a 'longstanding political-science standard for 'major bills''. Trump signed 24 executive orders in his first 100 days, the most executive orders of any president since World War II.