Luna Watch

During the fall of man, war spread out across all its planets and cities. Many thought they alone could pull us back from the brink, and attempted to put their money where their mouth was with the most advanced weapons we had ever seen. Weapons that could wipe cities off the map, slay vast armies single-handedly, even crack a planet. Or maybe it's moon?
Whatever it was that cracked a sliver of the earth's moon off is unknown, hopefully, there isn't anything sitting out in the world that could do it again, though I'd hazard to say that we haven't earned that luck back quite yet. Looking into the sky, we can still see the (now) two pieces of sister Luna, barely held together by the larger sections weakened gravity. 
Throughout the year, the two pieces vary in distance from one another. Making the gap more or less noticeable depending on the night, but there's only one day a year that Luna looks whole again and it doesn't go unnoticed by anyone walking down on the scarred earth. 
Across the world people come together in boisterous celebrations. Alcohol and food flow freely from houses and restaurants, and work slowly grinds to a halt throughout the day as the hour in question grows closer. Unexpectedly, the Luna Watch festivals are some of the only times and places that both sides of humanity, Organics and Synthetics, can be seen celebrating together.
As day becomes night, the streets will fill with crowds as they jostle to get a better view. Highrises, restaurants with balconies, and glass-topped skyscrapers will be rented out months in advance, just so that they can be used to see the conjoining of the long lost puzzle pieces.