This is the base class for any time measurement
and calendrar information. It defines all the
things you can do with a time range, any time
period.
A TimeRange doubles as both a fixed period in
time, and an amount of time. For instance,
a week plus a day moves the week-period one day
ahead (unaligning it with the week period,
and thereby reducing it to just 7 days),
no matter when in time the actual day were.