These two files solved my clock problems on an AT. One routine fixed
the problem of the date not advancing at midnight, and the other fixes a
bug introduced by the first(?), namely, not reading the CMOS clock when
the system is booted up.

Put CLOCKF.SYS in whatever directory you keep your drivers, e.g.
C:\DRIVERS, and include the following in your CONFIG.SYS:

DEVICE=C:\DRIVERS\CLOCKF.SYS

Put SETCLK.COM in a directory in your executable path, and execute
SETCLK within your AUTOEXEC.BAT.

I grabbed these files quite a few months ago and suspect that only the
older AT systems are affected by the clock problems as I don't hear too
many requests for the solution anymore. I'm sorry I didn't keep all the
appropriate credits for these files, so there are two unrecognized
developers out there that have donated their efforts to these solutions.