P.R. Laws tit. 31, § 3048
The effects of a conditional obligation to give after the condition has been fulfilled shall retroact to the day on which it was constituted. Nevertheless, if the obligation should impose mutual prestations on the parties concerned, the fruits and interest for the time during which the condition has been pending shall be understood as compensating each other. Should the obligation be unilateral, the debtor shall become the owner of the fruits and interest collected, unless by reason of the nature and circumstances of the obligation it must be inferred that the will of the person constituting it was otherwise.
In the obligations of doing or of not doing, the courts shall determine in each case the retroactive effect of the condition fulfilled.
History —Civil Code, 1930, § 1073.