As part of the POSIX standards for 64-bit computing, known as LP64 (64-bit Longs and Pointers), the time_t data type for file times is expanded to 64 bits in z/OS® V1R6. The current signed 31-bit data type will go negative in 2038. Because the 390 system clock will wrap in 2042, there is an issue for PFSs that store time in STCK format.

The z/Architecture® has a 128-bit STCKE that adds one byte to the left of the current 8-byte format; that is, it has five bytes of "seconds", and goes to about the year 36765. An 8-byte POSIX time value goes far beyond that. A 9-byte time field, or the left 8 bytes of the new STCKE, would hold any real times, and an 8-byte POSIX format field would hold anything that could be set by a user.