When Stephen Hawking hosted his legendary 2009 reception for time travelers at the University of Cambridge, he published the invitations after the party was over, testing whether future travelers could navigate backward across time. Yet Hawking’s invitation listed only conventional surface coordinates and civil time. In a relativistic universe, those coordinates are fatal: Earth rotates, hurtles along its heliocentric orbit at 30 km/s, and races through the galaxy. Plugging surface numbers into a hypothetical time machine materializes the traveler thousands of kilometers out in the freezing vacuum of interplanetary space, or causes a devastating kinetic collision with a moving planet. This is a thought experiment; we are not claiming backward time travel is possible. The Abrams Event Address (AEA) directly extends Hawking’s thought experiment into a universal spacetime addressing standard. The real problem is unambiguous event tagging across bodies, frames, and time scales. Grounded in the foundational principle that addresses come before transportation, AEA treats four-dimensional spacetime as an addressable namespace. The AEA address synthesizes the seven physical invariants required to locate any event in the cosmos into a single, deterministic coordinate string: central celestial body, continuous atomic time, astronomical reference frame, three-dimensional position, velocity matching, attitude orientation, and an unkeyed SHA-256 integrity digest (detects accidental change; authentication belongs to higher layers). Demonstrating the protocol with worked canonical addresses for Hawking's 2009 reception in Cambridge and NASA’s Perseverance touchdown on Mars, this paper establishes the universal destination standard that must precede all physical transportation across space and time. A reference implementation is provided, with embedded software architecture detailed in later sections.