The Uniform Time Act of 1966 standardized time zones and daylight savings in the United States:
It is the policy of the United States to promote the adoption and observance of uniform time within the standard time zones prescribed by the Act entitled “An Act to save daylight and to provide standard time for the United States”
Prior to that each state picked their own schedule for moving clocks forward and back. Now it is overseen by Department of Transportation.
This is not my favorite weekend. I’d be happy to not change my clock again.