I'm guessing it's Tuesday night. When I was on the Majesty, formal night was the second night, but the itinerary was slightly different. The embarkation and debarkation days were the same, but we did Nassau, then CocoCay, then Key West.
Assuming the ports of call don't make any difference in determining that decision, then I would assume it's Tuesday night. It definitely will not be Monday night or Thursday night, so it's either Tuesday or Wednesday.
2007 - Majesty of the Seas (Bahamas)
2009 - Enchantment of the Seas (Western Caribbean)
2010 - Freedom of the Seas (Western Caribbean)
2013 - Golden Princess (Alaska, roundtrip from Seattle)