Md. Code, Estates and Trusts § 14.5–605

A person shall commence a judicial proceeding to contest the validity of a trust that was revocable at the death of the settlor within the earliest of:

(1) 1 year after the death of the settlor; or

(2) 6 months after the trustee sends the person a copy of the trust instrument and a notice informing the person of the existence of the trust, the name and address of the trustee, and the time allowed for commencing a proceeding.