It was the other way around. Works weeks were 48 hours or more until Henry Ford enacted a five-day 40-hour week in his factory in 1926[0]. Later, in 1939, laws were passed that officially established the new only-40-hour week as the norm, with 32 hours as the official mark of full- vs part-time, and anything over 40 being deemed "overtime."

At least in the United States, that's the trend.

0. https://www.truthorfiction.com/henry-ford-invented-the-5-day...