WCAG itself is a technical standard published by W3C and does not create a universal legal deadline.
Different laws, regulations, procurement rules and policies may adopt specific WCAG versions. The U.S. ADA Title II web rule uses WCAG 2.1 Level AA. Current UK public-sector guidance refers to WCAG 2.2 AA. Section 508 uses WCAG 2.0 Level AA for many ICT requirements.
Which version should teams test against?
Use the version required by the applicable law, policy, contract or procurement request. Where no external requirement names a version, WCAG 2.2 AA is often a strong technical target because it includes newer success criteria while preserving the structure of earlier versions.
Related: WCAG 2.1 or WCAG 2.2: which version should your organization test?.