GN_Gmd, Get (read) the current machine system date in internal format

RST 20H, DEFW $1809

IN:

     DE = 0, not allowed.
     DE = 1, not allowed.
     DE = 2, return system date in ABC.
     DE > 255, pointer to write machine date at (DE).

     If DE(in)>255 then DE = DE(in) + 3; ABC = ABC(in)
     If DE(in)<255 then DE = DE(in); ABC = result

     ......../IXIY same
     AFBCDEHL/.... different

Bugs:
 

Related calls:

GN_Dei, convert zoned format date to internal format
GN_Die, convert internal format date to zoned format
GN_Gdt, convert an ASCII string to an internal binary date
GN_Pdt, write internal date as ASCII string
GN_Pmd, put (set) machine date