According to our release support policy (https://doc.qubes-os.org/en/latest/user/downloading-installing-upgrading/supported-releases.html), stable Qubes OS releases are supported for six months after each subsequent major or minor release (https://doc.qubes-os.org/en/latest/developer/releases/version-scheme.html). This means that the EOL date for Qubes 4.2 was set at the time Qubes 4.3 was released by adding six months to the Qubes 4.3 release date. Qubes 4.3.0 was released on 2025-12-21 (https://www.qubes-os.org/news/2025/12/21/qubes-os-4-3-0-has-been-released/). Adding six months to this date gives us 2026-06-21, which is Qubes 4.2’s EOL date. Since the EOL date of 4.2 was determined at the time 4.3 was released, we also included this information in the 4.3.0 release announcement (https://www.qubes-os.org/news/2025/12/21/qubes-os-4-3-0-has-been-released/#support-for-older-releases).