IBM DOS 7 and PC DOS 2000

UPDATE: a patch has been released that fixes this issue on PC-DOS 7. See below.

An issue has been discovered with IBM DOS 7 / PC DOS 2000 involving compatibility with V20-based CPUs and INT 1Ah (functions AH=3 and 5) support, where due to a bug in the byte-to-BCD conversion code in this version of DOS, date and time are written incorrectly to the real-time clock. This only affects using DOS to set the clock - reading the clock is unaffected.

Possible workarounds are:

1. Use the program for that RTC to set the clock initially. DOS 7 can read the clock correctly.
2. Use any other version of PC or MS-DOS 3.3 or higher, or FreeDOS.
3. Use the patched version of PC-DOS 7 that fixes the AAD 16 issue: VCFed thread link.