So I've been reading a lot of lore articles about TES, and it seems that each Daedric Prince has a specific date they can be summoned on (some have other times they can be summoned as well). This would be pretty fun to have in the next game, I think. Instead of finding a hidden shrine, or speaking with a random NPC, you should have to wait until a specific date (or event) to summon them on your own, wherever you are. Doing Daedric quests this way, you could also call them forth once a year (or more, again depending on the Daedra) just to shoot the breeze

yes it would be cool but having to wait in-game days for an event is pointless in an open world game.

This is how it worked in daggerfall though it was a bit of a pain keeping up with dates.

not to mention that the gates to oblivion are closed so even summoning a deadric prince they are limited to where they can go

How it worked:

1. Wait & wait for specific date.
2. Spend 200k (discount if certain tasks done/witches) to try and summon a specific prince.
3. Get trolled by Sheogorath appearing instead.
4. I hope you remembered to save!

Still, it seems very weird to me how easy it is to get involved with Daedra in the game. Without giving spoilers, just doing things a warrior would naturally do and helping the less fortunate will lead to encounters with daedra princes.

Yep, Azura's Star in Morrowind was sorta like that wasn't it? Had to wait for a certain time and date for the door to her shrine to open up?

Yeah had to be six am or pm if i remember right.

Do you have any idea how pissed off I would be if I was like an hour late then I'll have to wait a whole ingame year?

I don't think summoning days would work with the current setup for TES games. They made sense in Daggerfall, because in Daggerfall you literally burned in-game days and weeks fast-travelling, waiting a year wasn't so bad as long as you paid attention to the in-game clock and budgeted your time. (You could also literally spend in-game days in a single dungeon, with mages settling down for naps when their magicka ran out, for example, or warrior types sleeping in the dungeon when their health was low, or simply being lost in the dungeon for days) In the modern days of Morrowind-Oblivion-Skyrim, you simply don't burn that much time doing anything. The Main quest of Oblivion can beaten before you ever get to Frostfall, as long as you don't get too distracted with side quests or guilds, and the game starts pretty close to the end of Last seed. In Daggerfall, meanwhile, your character will spend months of time merely fast-traveling during the MQ.

Unless they change up the game mechanics to allow more frequent passage of large amounts of time, summonings days would have to be more common in order to work as a game mechanic.