Timebomb

Timebomb or time bomb is a software mechanism that renders a computer program unusable after a pre-set period of time. It is commonly seen in pre-release software, where it is used to discourage users from holding onto outdated testing versions.

Windows
In Windows 9x-based builds of Windows, the timebomb is activated by. Once the timebomb is triggered, Windows will display a message on boot saying the pre-evaluation period has expired. Windows will then immediately shut down and will not boot until the operating system is reinstalled with the correct BIOS date ( patches itself on disk to infinite loop). Windows 95 build 216 is the first known build to include a timebomb.

In NT-based Windows versions, once a timebomb is triggered, the  bugcheck is used to periodically reboot the system. The first build to include a modern timebomb was Windows 2000 build 1627.1, although the Japanese and Korean pre-release versions of Windows NT 3.5 include a warning message box telling the user to install a retail copy of Windows after a certain date, unlike any other builds from the era.

Some builds between Windows 8 build 7850 through 8888 (win8 gdr soc intel), as well as all the fbl_partner_eeap builds of Windows 10 and some builds of Windows 8.1 contain broken timebombs and thus the timebomb won't activate if installed on the current date. However, installing these builds on the current date renders Windows unactivated, preventing access to personalization options in Settings, and prevents changing the desktop wallpaper in Control Panel without a third-party tool such as DeskImg or ProductPolicyEditor.

Most builds of Windows 10 version 1507 and 1511 are flightsigned (file signatures take certificate expiry time into account). Should the timebomb activate, the boot loader will be rendered non-functional due to expired certificates.

macOS
Mac OS X Public Beta is the only known version to include a timebomb. While the timebomb didn't allow the user to log into the user interface, it didn't affect the Darwin kernel or any other components not related to the Aqua interface.