at time
returns an incremental that is Before
when now () <= time
and
After
when now () >= time + alarm_precision
. When now ()
is between time
and time + alarm_precision
, at time
might be Before
or After
, due to the
fundamental imprecision of the timing wheel. One is guaranteed that an at
never
becomes After
too early, but it may become After
up to alarm_precision
late.
after span
is at (Time.add (now ()) span)
.