A gift of liberty by will is not necessarily absolute and immediate: it may be subject to a condition or deferred to a future day. Pending the event the man is a statuliber: we have already considered his position and have now to discuss the other questions affecting these modalities.

Where the liberty is deferred to a certain future time, it is said to be subject to dies certus. If the words ad annum are added, e.g. ad annum liber esto, they are construed as meaning “at the end of a year.” If the words are ad annos decem, they are treated as swpervacua. A gift of freedom intra annum post mortem entitles the donee to liberty at once. The rule is attributed to Labeo, and is declared to be justified by him as an inference from the rule that where the gift is: Let him be free si heredi intra decimum annum decem dederit, the man is free if he pays at once. It is plain that this does not justify the rule. The one rule says merely that to impose a time within which the condition must be satisfied is not to impose dies in addition to the condition: it leaves the choice of time within a certain limit to the slave himself. The other does not: it does not say who is to have the choice of time, and the actual rule is a case of favor libertatis. We saw that ad annum meant at the end of the year.