Master MOS Y2K in OSWORD 14
                     ===========================

The only part of the Master MOS that does anything with centuries is the
string returned by OSWORD 14,0. It is hard-wired to 19xx. Anyway, code
calling OSWORD 14,0 should always be checking the returned result anyway in
case there is no RTC at all, with something like:

  X%,Y%=>control block
  A%=14:?X%=0:CALL &FFF1
  T$="":IF ?X%:X%?24=13:T$=LEFT$($X%,11)+STR$(26-(X%?13)DIV8)+$(X%+13)
  REM T$="" if no RTC, else T$=time string with correct century

There's enough space in MOS 3.20 and MOS 3.50 to squeeze in a full 19xx vs
20xx year check, but - the further into the 21st century we get, the more
remote is the need for OSWORD 14 on live hardware to return the year as
19xx, so why not hard-wire it to 20xx.

This is easily done with:

MOS 3.20: 9881 change to &20
MOS 3.50: 9664 change to &20

However, if you do want to patch the MOS to return both 19xx and 20xx, it
can be done with:

Patch MOS 3.20:
987D: JSR &B8DF
9880: NOP:NOP

B8DF: JSR &9890
B8E2: CMP #&38
B8E4: LDA #&19
B8E6: BCS &B8EA
B8E8: LDA #&20
B8EA: RTS


Patch MOS 3.50:
9660: JSR &FB21
9663: NOP:NOP

FB21: JSR &9673
FB24: CMP #&38
FB26: LDA #&19
FB28: BCS &FB2C
FB2A: LDA #&20
FB2C: RTS