When contracts become void which are contingent on happening of specified event within fixed time

When contracts become void which are contingent on happening of specified event within fixed time.—Contingent contracts to do or not to do anything if a specified uncertain event happens within a fixed time become void, if, at the expiration of the time fixed, such event has not happened, or if, before the time fixed, such event becomes impossible. When contracts may be enforced which are contingent on specified event not happening within fixed time.—Contingent contracts to do or not to do anything if a specified uncertain event does not happen within a fixed time may be enforced by law when the time fixed has expired and such event has not happened, or before the time fixed has expired, if it becomes certain that such event will not happen.