The world's going to end in one week. It's been doing that for a while now.
Someone in Equestria's broken the world. They've taken time along with it, trapping everything into a single, indefinitely repeating week. Only the elements' bearers move forwards in time, but they've got problems of their own. For each cycle drains their talents from them, each conversation twists old friends into enemies, and not a single one of them knows how to save the world. Some of them have even stopped trying.
And then Twilight finds a way. All that's left to do is gather everyone back together.
Story arcs written about an apocalypse cycling in perpetuity and the effect it has on Equestria. Not as dark as it tries to be.
Additional: Story formatted to look its best in Font Serif, Size Normal, Colour Medium-Dark, Paragraph Spacings 1.2; this as the banner image; no interactive pony, Snow Default, css color #8c8691, Background Pattern Stars and Background Image Night Town . Reading otherwise will expose you towards rogue spacings, silly typography and a severe lack of Luna.