Timespan-class
class. An Interval object
records one or more spans of time. Intervals record these
timespans as a sequence of seconds that begin at a
specified date. Since intervals are anchored to a precise
moment of time, they can accurately be converted to
Period-class
or
Duration-class
class objects. This is
because we can observe the length in seconds of each
period that begins on a specific date. Contrast this to a
generalized period, which may not have a consistent
length in seconds (e.g. the number of seconds in a year
will change if it is a leap year).Interval class objects have two slots: .Data, a numeric object equal to the number of seconds in the interval; and start, a POSIXct object that specifies the time when the interval starts.