Granted they say there is no general way to create the night / day mechanic without devoting lots of cards to that day / night mechanic to make it play properly riiight? But one Vangaurd card that is tourney legal would be an answer.
Hour of Fate Vangaurd T: Game state is Day. T: Game state is Night. 5: untap 'Hour of Fate.'
Hour of Fate is removed from the game.
Then the hosers:
3B Aura : Each player loses 2 life during thier upkeep if the control a Vangaurd card.
4W Instant : Turn target Vangaurd card upside down until end of turn.
10GG Sorcery : Destroy target Vangaurd card.
2U Sorcery : Target Vangaurd card's abilities can not be played next turn.
3RR Instant : When a Vangaurd card is tapped that player sacrifices two lands.
T: Game state is Day.
T: Game state is Night.
5: untap 'Hour of Fate.'
Hour of Fate is removed from the game.