When does Pokérus in Pokemon Moon have a chance of being cured: midnight game time or midnight system time?

Summary

I haven't played a standard pokemon game since Generation 1 until recently when I picked up Pokemon Moon. A friend traded me some pokemon infected with Pokérus to help me get started, but I accidentally let all my infected pokemon become immune, and I'm not sure exactly when the immunity triggered.

Findings So Far

According to this IGN article:

"After one to four days (at midnight), Pokerus will no longer be contagious..."

However, since Pokemon Moon is timeshifted by 12 hours with respect to the 3DS system time, I am not sure if "midnight" in this context would be applied based on the 3DS system time (i.e. "real life time") hitting midnight; or "midnight" in Pokemon Moon which would be Noon IRL.

I also tried searching existing questions, but couldn't find any results that matched my question at the time of writing this question.

Educated (unconfirmed) Guess

If I had to guess, I'd lean towards it triggering at midnight based on system/real-life time; just because the player is more likely to be asleep rather than at noon; but I've been unable to find confirmation of this.

Can anyone confirm the exact timing that Pokérus has a chance of becoming cured in Pokemon Moon?

The Pokérus is working with the in-game time. Reading the wiki page about Pokérus:

Whenever the game's internal clock strikes midnight, every currently infected Pokémon in the player's party has their Pokérus value decreased by one. Once the Y value reaches 0, the Pokémon will be cured of Pokérus.

So for Pokémon Moon, you have to take the 12 hours shift in account. You can get the actual in-game time by asking the coffee shop vendor in any Pokémon Center.