Del. Code tit. 12, § 3331

In the construction or interpretation of any will or trust, or other governing instrument, if a determination is to be made whether the beneficiaries entitled to receive a distribution from an estate or trust are to be determined at an earlier or later time, such beneficiaries are to be determined at the earlier time unless the will or trust, or other governing instrument, expressly provides that the determination shall be made at the later time.