Short Answer:
"Y2038 refers to an issue related to the way time is handled by computers. Time is often represented as the number of seconds since Jan 1, 1970. Whenever a 32-bit signed integer is used for this, the maximum value that can be represented is +/- 68 years, 19 days from the epoch, which corresponds to Jan 19, 2038. What happens after that is system dependent, but generally not good. A computer may act as if its time got reset to Dec 1901, or possibly to the epoch of Jan 1, 1970. It may give unexpected results or crash.
Basically, any software that uses time in any way may potentially have Y2038 issues. While only a small percentage of each software component is typically affected, this is still enough to cause many problems. Embedded systems with 32-bit cores and computers running 32-bit versions of Linux and Windows and are particularly at risk, but even 64-bit computer systems may have problems. In 64-bit computer systems, time can be represented in 64-bit integers, but Y2038 issues may still exist in applications, device drivers, databases, storage systems, and network protocols."
More Information - https://y2038.com/faq/