This wasn't even a day. It was literally around 10 to 11 hours.
The huge irony being that Bride Lucina didn't even start with Fire Emblem Warriors, made by Koei Tecmo who are known for their fanservice. It started with Project X Zone 2,
Made by Monolith Soft.
Although to be honest, besides X Zone 2, I think the fact that there was the Bride Event in Heroes and a Bride Lissa in the Cipher card game may have helped in deciding Bride Lucina as a costume for her in FEWarriors. Although the other possibility is that the Bride class is a favourite among the IS staff.
And I'm not counting Fire Emblem Awakening as that's more class change shenanigans rather than a costume.