It wwould/should be in the players guideI still have a Purify Blood potion tag.
I figured that it is like the Chinese calendar, Mayan Calendar or any other such calendars. That there are regions that may have their own calendar - especially remote areas that have a calendar but not a lot of contact with the rest of Fortannis. But feel that there is a "Fortannis Year" that is currently 617.
I can only find one reference to a year in the current (and the last three) rule books and that is under "How to Get Your History Rejected" where it says "...if you write that the Duke killed your father in the year 597..."