This is going to sound totally silly, but I actually had a concept for an RPG story once that had the very same premise as this game, with the wedding opening being interrupted by an attack and setting up the premise for the game. Damn, I guess I was on to something! (No, definitely no...)
Anyway, I definitely have to check out this game to see how they developed this idea.
One thing I wanted to mention about the issue of the multiple possible heroines and the dating sim aspect... with a title like "Time and Eternity", I imagine the concept of alternate timelines may very well come into play here. Not sure if it could involve a "change the past to change the future" sort of scenario, or who knows... but I wouldn't necessarily take it for granted that they literally mean "the wedding is called off and the protagonist falls in love with someone else, quasi-cheating on his first love". With this theme and premise, I imagine they'll try to keep a lot of aspects of the story mysterious until the game is released.