'Add a duration to an Epoch.
= INPUT VARIABLES
- rhs    The Epoch to subtract.
= RETURN VALUE
- Returns the difference of ourselves and the input Epoch.'

def __add__(self, rhs):

    t = self
    if (self._frame != rhs.frame()):
        t = self.convert(rhs._frame)
    sec = (t._seconds + rhs.seconds())
    return Epoch(t._frame, sec, t._jd)
