Heading down the rabbit hole…
Everything that happens in Half-Life / Portal, 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.