I'm sure such software exists – back in the day it was sometimes a useful means of circumventing software that would stop working after thirty days. Unfortunately I cannot recall what any of those programs were called. 😒

I may take a whack at making my own, although I'm not much of an assembly programmer. I think these resources may help me:
http://spike.scu.edu.au/~barry/interrupts.html#ah2a
http://www.fysnet.net/tsrdemo.htm#below2

Here's a simple TSR program, pass it the number of years (1-99) to subtract, e.g. YEARSUB 20. It handles the INT 1A/04 and INT 21/2A functions, but does nothing about reading the date through CMOS registers. Source code included.

Thanks! It seemed to work for the games' setup when I ran in a command.com prompt (versus a cmd.exe one). I'll find out tomorrow if it's working for the games themselves.

Edit: What assembler/linker did you use?

HunterZ wrote:

What assembler/linker did you use?

A86, but MASM or TASM and their linkers should have no problem with it, selecting tiny model with switches if need be.

Thanks.

Looks like it's working, as the affected games ran their daily maintenance when logging in just after midnight. Previously they couldn't tell that the day had rolled over because the year was off the end of what they could track. Now they think it's 1995, which is about the last time that I actually played them 😀