What Is Q-Day? The Date Quantum Computers Break Classical Encryption Category : Education What Is Q-Day? The Date Quantum Computers Break Classical Encryption 7 min read What Q-Day Means Q-Day (sometimes Y2Q) is industry shorthand for the moment a Cryptographically Relevant Quantum Computer (CRQC) exists. A CRQC can run Shor's algorithm on real-world cryptographic parameters like RSA-2048 or ECDH P-256. Q-Day is not a fixed date; it is a probability distribution estimated by expert surveys. Why the Term Is Useful Q-Day gives non-technical stakeholders a concrete handle for an otherwise abstract threat. It also communicates urgency: Q-Day is already inside the Mosca threshold for most regulated data. Current Expert Estimates Global Risk Institute Quantum Threat Timeline 2025 : 10-year likelihood of CRQC between 28 percent (pessimistic) and 49 percent (optimistic), the highest 10-year range in the survey's seven-year history.…