In 1919 Sam sees a notice outside the bar stating it was closed due to violations of the National Prohibition Act. The actual law implementing the prohibition of intoxicating beverages was the Volstead Act and while it was passed in October 1919 it did not go into effect until January 17, 1920 and enforcement did not begin until then.
If Sam came from and returned to 2019, then Evelyn was transported to 2019. Sam Jr. would have been 5 years old in 2024 or 2025. Not 2034 as Evelyn's poster on the wall suggested.