Fix a rounding/off-by-1 error in the calendar.
Fix a rounding/off-by-1 error in the calendar.

git-svn-id: 53f7d0dd214ba14810b120d5ecb1d5e857f3a22b@24 3d0d11d8-4750-0410-97fd-29bed8d48615

knipknap/SpiffGtkWidgets,xrg/SpiffGtkWidgets