What is the most likely cause of a computer hanging after POST, indicated by a date several years behind in UEFI setup?

The situation described points to an issue with the motherboard battery, which retains the BIOS/UEFI settings, including the system date and time. If the date in the UEFI setup is significantly behind, it often indicates that the battery is failing or has already failed, leading to the loss of current time and date information. This can disrupt the boot process, as the system relies on accurate timestamps for various functions, including scheduling tasks and managing hardware. A failing battery could also result in the system not retaining necessary configurations, causing it to hang after the Power-On Self-Test (POST) as it struggles to proceed without valid settings.

In this context, while a corrupted operating system could lead to boot issues, it is less likely to manifest as an incorrect date in UEFI. Similarly, a faulty hard drive might cause boot failures or hanging but wouldn’t specifically result in an artifact like an incorrect date. As for a malfunctioning power supply, while it can lead to erratic behavior or failures in powering components, it does not directly affect the UEFI settings like the motherboard battery would. The date being years behind aligns closely with the symptoms of a failing battery, confirming that option C is the most likely cause.