'See L{twisted.internet.interfaces.IReactorTime.callLater}.'

def callLater(self, when, what, *a, **kw):

    dc = base.DelayedCall((self.seconds() + when), what, a, kw, self.calls.remove, (lambda c: None), self.seconds)
    self.calls.append(dc)
    self._sortCalls()
    return dc
