Heading down the rabbit hole…
Everything that happens in Mass Effect, in story order. Story years, until someone sets up this universe’s own calendar. For when its stories came out in the real world, see the real-world timeline.
Help build it: first say how time works in this universe (story years, days, before/after an event, or ages), then add the moments that happen in it.
Know when these happen in the story? Sign in to place them.