NIGHT TIME!!

[Elexia]

Yeah, maybe. But I didn't played XI so I wouldn't know about this
That was just something that came to me, since I played a lot in Monster Hunter.

Here's an example:

Days of the week affected your spell potency along with weather, so if it's Darksday, you'd take a slight hit on your curing spells and on lights day with double light weather (auroras) you'd get a crazy boost to your light spells (offense/defense) in the right conditions.

In terms of moonphases, there's a Blue Mage spell called Plenilune Embrace which heals the party member and gives them attack and magic attack boosts that varied based on moon phase, given the name. Stuff like that is affected by moon phases and the days but people link it mostly to crafting.

You have no idea what you're talking about:

Kira seen FFXI and immediately went into "NO!" mode lol. The only issue was how it was presented to us compared to XI being more straight forward about it.