Period and Duration are not just alternatives, they work very
different. Duration is designed to work in exact measurements in
seconds and nanoseconds. However, Period calculates Days and Months
conception-wise ... that is some months can be 28,29,30, or 31 days,
and days can be 23, 24, or 25 hours long. So, if you add a Period of
1 Day, you always going to end up the next day same time. However, if
you add a Duration of 1 day (24 hours), then you can end up one hour
before or after, or same time depending on whether Daylight Saving
Time change was crossed