Hi @Archaeo80, I notice there are some significant deviation between the predicted date of rare quests compared to the actual date. The Shiloh Desert was predicted to be at 22th July but eventually ended up at 13th July. Could it be that in your calculation, the distance between each rare quest is around 10-11 days?
I have done some calculation which conclude in rare quests appear around every 9 days:
The cycle length from Shiloh to Shiloh is around 61.6 days. As there are 7 different rare quests, it means rare quest appear around each 9 days.