Unix epoch

The Unix epoch is the measurable range of time supported by Unix-based operating systems, such as Linux, and derivatives of Mac OS X (including iOS, iPadOS, macOS, and watchOS). The epoch on these systems begin at midnight on January 1, 1970. An error in this time value can cause a system to report the date as December 31, 1969.

Date ranges
The epoch of early 32-bit Unix-based systems and hardware (such as Mac OS X prior to 10.6, or Apple A6X and earlier) ends on January 19, 2038 at 03:14:07.

Modern Unix-based systems and hardware (such as macOS since 10.6, the Apple A7 processor and later) have widened the time value to 64-bits, delaying this issue by billions of years.