Why when year is less than 1884, it remove few milliseconds?

Question

DateTime start = new DateTime().withYear(1884);
System.out.println(start);
System.out.println(start.minusYears(1));

Output

1884-01-         


        

Answer 1

The standard time has been adopted by the US during this year.

1883: U.S. and Canadian railways adopt five standardized time zones to replace the multiplicity of local times in communities across the continent. Everyone would soon be operating on "railroad time."

Source

Wikipedia page about Standard Time