I would like to see a calendar in the game, so we can see when the seasons start and end. Farmers would like that, and it might be interesting for adventurers in the wild also.
Personally to me it's more for roleplaying purposes.
1: Plan holidays or days of mourning.
2: One day off, for the shops, so NPCs can have some quality time with the family.
3: Plan stuff like military exercises.
4: Religious Holidays.
5: Remember certain events like the death of someone in a high position.
6: Remember the date you was married or born.
In general so we know what day it is, and not every day is just a number. An ingame timer, so when I log on, I know what day it is in Elyria with an alarm for certain events like harvest day or tax collector day.
This looks like something important, so everybody in the County, Duchy, Kingdom knows if it's a holiday or some sort.
It connects you to everybody in the area, county. You all have something in common, even the NPC's.