No, it is not true that childhood ends at 25 according to the Obamacare legislation (Affordable Care Act). The Affordable Care Act (ACA) is a comprehensive healthcare reform law in the United States that was signed into law in 2010. It introduced several significant changes to the healthcare system, but it does not define when childhood ends.
The ACA does include a provision that allows young adults to stay on their parents' health insurance plans until they turn 26 years old. This provision was implemented to provide young adults with more access to affordable healthcare coverage as they transition into adulthood, particularly during a time when many might still be pursuing education or starting their careers.
So, while the ACA extends healthcare coverage under parents' insurance plans until the age of 26, it does not legally define the age at which childhood ends. The legal age of adulthood typically varies by country and is often set by other laws and regulations, such as age of majority or voting age. In the United States, the age of majority (when a person is considered a legal adult) is 18 years old in most states.