Duration is an S4 class that extends the Timespan-class
class.
Durations record the exact number of seconds in a time span. They measure the
exact passage of time but do not always align with measurements
made in larger units of time such as hours, months and years.
This is because the exact length of larger time units can be affected
by conventions such as leap years
and Daylight Savings Time.
Durations provide a method for measuring generalized timespans when we wish to
treat time as a mathematical quantity that increases in a uniform, monotone manner
along a continuous numberline. They allow exact comparisons with other durations.
See Period-class
for an alternative way to measure timespans that better
preserves clock times.
Durations class objects have one slot: .Data, a numeric object equal to the number of seconds in the duration.