diff -D isn't showing any changes but history does

[Wayne_Johnson]

I'm trying to show all changes made to a directory over the last few weeks.  I
do:
$ cvs history -c -a -D 2001/06/20 bsp3/src/kxc/pipe

M 2001-06-21 22:06 +0000 mryan 1.20.2.1    kxcscsdm.txt bsp3/src/kxc/pipe ==
<remote>
M 2001-06-29 15:07 +0000 mryan 1.1.1.6.2.1 kxclmana.c   bsp3/src/kxc/pipe ==
<remote>
M 2001-06-29 15:07 +0000 mryan 1.1.1.5.2.3 kxccmsga.c   bsp3/src/kxc/pipe ==
<remote>
M 2001-06-29 15:07 +0000 mryan 1.8.2.1     kxczflua.c   bsp3/src/kxc/pipe ==
<remote>
M 2001-06-29 15:07 +0000 mryan 1.9.2.1     kxchfnca.h   bsp3/src/kxc/pipe ==
<remote>
M 2001-06-29 15:07 +0000 mryan 1.5.2.1     kxchfida.h   bsp3/src/kxc/pipe ==
<remote>
M 2001-07-05 18:37 +0000 mryan 1.3.2.1     kxcbmvs.mak  bsp3/src/kxc/pipe ==
<remote>

and I see plenty of changes, when I do:
$ cvs diff -D2001/06/20  -Dtoday
                                                                                
              

cvs server: Diffing .
cvs server: Diffing jcl
cvs server: Diffing lked
cvs server: Diffing lkedc
cvs server: Diffing lkedc/x
cvs server: Diffing mvscobol
cvs server: Diffing mvsparm
cvs server: Diffing os4cobol
cvs server: Diffing rexx
cvs server: Diffing test
cvs server: Diffing test/mvscobol
cvs server: Diffing test/os4cobol

Nothing?  What am I missing.