I would think seasons are the driving reason for an adjusted calendar. Any rotational tilt from the orbital plan will induce seasons. Every planet in our system has seasons, even the gas giants. That will have a cyclical effect on climate. Even in a sealed habitat, thermal regulation and solar power will be affected. The local year will also have an affect on interplanetary travel because, spatially, a day of the year is a specific place in space rather than a specific time. So a local calendar would provide a conversion.
As for a universal calendar, you’re right that it doesn’t fix anything. Instead of a calendar that works in one place and not 999 other places, a universal calendar would “not work” in 1000 places and work correctly in zero places. We already do something similar with global/space operations: make everything UTC time zone. While yes, it’s practically just prime meridian time, it doesn’t do daylight savings.
I’m curious how this is playing out. A fair number of details are present on the game’s item already. The barrel stripe, the upside-down spade with a circular element, and the barrel spade.
https://destiny.fandom.com/wiki/Ace_of_Spades_(Destiny_2)
That’s not to deny the direct copy of this specific design, but rather ask how much can an independent artist claim on what appears to already largely part of what already exists within the game’s IP.
That being said, the reddit thread where the artist posted this originally has an edit stating Bungie reached out, handled it well, and will be sharing details later.
https://www.reddit.com/r/DestinyTheGame/comments/1fe9p6h/soothe_nerf_ace_of_spades_designer_stole_art_i/