I have seen this once before, but cannot re-create it now. Are you entering invoics for December? What default date are you using? Do you enter dates by typing them in, or popping the calendar with the down arrow key?

Do you get any error messages or other strange behaviour besides this?

Are you sure you have filled out all required fields correctly? Does the default date in the date field look ok?

How about typing the date in, instead of leaving it generated by the system? Does this work?

Unfortunately, we cannot fully support this version as it was discontinued quite a long time ago. I cannot duplicate this here with the current release of any of our Adagio modules, including the QIWIN successor, Adagio Invoices.

Check the Regional Settings in Windows to ensure that the 'long date' and 'short date' settings are using a 4-digit year perhaps.

Has anything at all changed on your system since this was working ok?

Have you tried doing a data-integrity check while logged in as a prior date? Were there any errors found?