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 It is commonly seen in pre-release software, where it is used to discourage users from holding onto outdated testing versions.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 one of the first builds 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.

Windows 8 builds 8102 through 8432 (fbl loc), as well as the fbl_partner_eeap builds of Windows 10 contain broken timebombs and thus the timebomb won't activate if installed on the current date. However, installing these builds on the current date prevents the user from changing the desktop wallpaper without a third-party tool such as DeskImg.

Most builds of Windows 10 version 1507 and 1511 are flightsigned (file signatures take certificate expiry time into account). Should the timebomb activate, the bootloader will be broken due to expiring 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.