When do I have to pay annual fees in Japan?

In Japan the annual fees for the first three years have to be paid in a lump sum within 30 days of the decision to grant. Subsequent annual fees are payable yearly in advance. For patent applications filed up to January 1996 (pre-grant opposition system), annual fees are due for each year from the date of publication of the examined document. For those filed from January 1996 onwards (post-grant opposition system), they are due on the anniversary of the first payment.