Sec 23. S.5.e.2.b:

A reserve pilot on long call will be notified of his assignment to open time under Section 23 N. or O. by one of 6 the following two methods:
1) telephone contact from Crew Scheduling.
2) electronic placement of a rotation or conversion to short call that is placed on his schedule prior to:
a) his release from a rotation, or
b) nine hours before the end of his last non-fly day (other than a vacation day) before an on-call day.

Definition of an x-day (which think can all agree is a non-fly day is: “X-day” means a 24-hour duty-free period at a pilot's base, on a reserve line." - Sec. 23 definitions.