U.S. Dep't of Defense, Instruction No. 5025.01, Part II (Oct. 28, 2007)
DTM: A memorandum issued ONLY for time-sensitive actions that affect current issuances or that will become DoD issuances, and ONLY when time constraints prevent publishing a new issuance or a change to an existing DoD issuance. DTMs establish DoD policy and assign responsibilities, or implement policies and responsibilities established in existing DoD issuances. DTMs concerning subjects requiring direct oversight by the Secretary or Deputy Secretary of Defense shall be signed by the Secretary or Deputy Secretary of Defense. DTMs that establish policy shall be signed by the Heads of the OSD Components. DTMs that implement policy shall be signed by the Heads of the OSD Components, their Principal Deputies, or the OSD PAS officials as authorized by their chartering DoDDs. DTMs shall not be used to permanently change or supplement existing issuances. They shall be effective for no more than 180 days from the date signed, during which time they shall be incorporated into an existing DoD issuance, converted to a new DoD issuance, reissued, or canceled.