In Mac OS X 10.5 Leopard's .Mac preferences (in System Preferences), your last sync may incorrectly be noted as having occurred "Today", even if you have not synced yet today.
If you sync again, the Last Sync notice in .Mac preferences will be updated as expected. If you have enabled displaying Sync Status in the Menu bar, the Sync menu item will show the last sync date correctly.
This document will be updated as more information becomes available.