Period vs Duration and daylight saving time transitions

Java separates two kinds of amounts of time. A Period is a date-based amount in years, months and days, such as "2 months and 3 days". A Duration is a time-based amount in seconds and nanoseconds, created from days, hours, minutes or seconds. The difference matters because a month or a calendar day does not always have the same length, while a Duration is always an exact number of seconds.