Playing with STCKCONV, STCKEVAL parameter

Has somebody already played with STCKCONV, STCKEVAL parameter?

1) With a tod value equal to x'FFFFFFFFFFFFFFFF':
         STCKCONV STCKEVAL=ETODSTMP,CONVVAL=TMEDTE,
                  TIMETYPE=DEC,DATETYPE=MMDDYYYY
ETODSTMP DC XL16'00FFFFFFFFFFFFFFFF00000000000000'


Resulting time & date:  23534737 09172042 (09/17/2042)

2) With a larger tod value:

         STCKCONV STCKEVAL=ETODSTMP,CONVVAL=TMEDTE,
                  TIMETYPE=DEC,DATETYPE=MMDDYYYY
ETODSTMP DC XL16'01000000000000001100000000000000'

Resulting time & date:  00000000 01011900 (01/01/1900)

Now, my impression was that STCKCONV with STCKEVAL
was especially designed to convert tod values larger
than 64 bits. Or did I do something wrong? Thanks.