faketime

Faketime is a command line tool that allows you to change the system time seen by other software without actually affecting the system clock. It is commonly used in testing and development scenarios where the software behavior needs to be checked under different time scenarios. With faketime, you can "fake" dates, times, and even time zones, enabling you to simulate specific time periods for testing purposes. The tool intercepts the system calls made by programs to get the current time and returns the desired fake time instead. Faketime works by using the LD_PRELOAD environment variable to load its shared library before any other libraries, ensuring that all calls to time-related functions are intercepted. The fake time can be provided as an offset from the real system time, allowing you to move forwards or backwards in time. This command line tool is available in various Unix-like operating systems, including Linux, macOS, and FreeBSD. It can be handy for testing time-sensitive functionalities such as scheduled tasks, time-based events, time zone conversions, and date calculations. Faketime is also useful for simulating past or future dates to reproduce bugs, simulate historical scenarios, or validate the behavior of time-dependent software features. However, it's worth noting that faketime doesn't modify system logs, network time synchronization, or affect software that relies on hardware clock readings directly.