Just been wondering about these. I know the current theory is that they drop from EP+ monsters with the element of the Geode based on the current day or weather (takes priority if there's any).
I think maybe it's not as simple as that and here's what I noticed...
Outside of Abyssea I haven't ever gotten a Geode based solely on the day of the week.
- Killed Sand Cockatrice in Cape Teriggan for 1.5 hours for Stingray trial. Got 1 Geode (Breeze) on Earthday during a 7-8 minute Wind Weather.
- Killed a few random things in Beaucedine Glacier/Xarcabard (S) while searching for Amphiptere's and got 2 Snow Geodes during Ice Weather (it was not Ice Day).
- Killed Lesser Colibri for 2 hours in Bhaflau. For about an hour during Earthday I got 1 Geode (Breeze) during a short spout of Wind Weather. I got 1 more Geode (Breeze) that was actually on Windday, BUT I was killing for the full duration of Windday and when I got the Breeze Geode, there was Wind Weather.
I was thinking at first that maybe Geodes only dropped based on the day of the week in abyssea, for the simple fact that weather does not exist in there. But then I was thinking of something different. Maybe Geodes only drop solely based on the day of the week IF the monster is above a certain level, like Level 80. That would explain why I got none from Sand Cockatrices or Lesser Colibri when only based on the day of the week, and would also explain why so many drop during Abyssea parties.
Just thought I post and see what people thought.