Only time will tell.

The Spu is cleverly saying that it opens/unlocks at a certain time, so either wait by it for a long time, or mess around with the time machine (if you have it unlocked) to figure out when it opens.

it unlocks at ~ 11:30-12:30 . I was kinda annoying trying to look this up earlier with no clear answer

Once the alarm clock unlocks, a light will shine in that section of the dungeon, which moves as the day goes on. Once the light is shining on that object, the minigame unlocks. It's hard to notice, because the first thing people usually do when entering that room is light it all up with the candle, which means you don't see the light anymore.

But yeah it's open from 12:31AM-6:05PM.

[Edit: Oh, also I guess I was replying to a necropost replying to questions from 7 years ago.]