Adding days to the Date portion of DateTime throws off the Time portion

Question

So I'm having an issue in Apex with the Date's addDays function. It seems that adding more than a certain amount of days throws off the time by one hour. It all seems so arbitrary so I'm wondering if this is a known thing in Salesforce or not.

DateTime aDate = System.now();
System.debug(aDate);
DateTime adjustedDate = 
DateTime.newInstance(aDate.date().addDays(4), aDate.time());

System.debug(adjustedDate);

Running that in an execute anonymous box outputs the following:
2019-03-05 17:44:28
2019-03-09 17:44:28

That's all good. The same date separated by four days and the same time. Just as you'd expect. But... adding five or more days causes behavior I can't wrap my head around.

DateTime aDate = System.now();
System.debug(aDate);
DateTime adjustedDate = 
DateTime.newInstance(aDate.date().addDays(5), aDate.time());
System.debug(adjustedDate);

This outputs the following:
2019-03-05 17:46:08
2019-03-10 16:46:08

It falls back by an hour. Any idea why or is this a known thing? I'm in central timezone so my time is actually -6 hours from the printed time.

Answer 1

Daylight saving time 2019 in central timezone will begin at

2:00 AM on Sunday, March 10

and ends at

2:00 AM on Sunday, November 3

All times are in Central Time.

:)