Be sure that you have examined everything in Robert's workshop and have talked to him completely.
You then should have the map of Carrion Woods.
You also should have read Countryside Festivals of Antiquity book at Celtic Corner and the paper inside Katherine's cookbook.
These should give the clues for the seasons.
- Now go to Millstone 1 and turn it to winter. Then look through the hole on the millstone to see the next millstone.
- then do spring.
- then do summer.
There are pictures of the millstone in the walkthrough. See if that helps.