Put it where it belongs.
Cards of things that happened, with the date hidden. Slot each one into the right place on the line — and whether you get it right or wrong, you find out when it really was.
Four cards start on the line for you, oldest at the top. Your card sits above it with a ? where its date should be.
Tap the + where you think it goes. Right, and it locks in. Wrong, and it walks to where it should have gone, so you see it either way — then it tells you something you probably didn't know.
There is no score and nothing to lose. Every card ends up on the line, and you go through the whole pack. It's here to teach you when things happened, not to beat anybody.
Packs count time in different ways — millions of years ago in one, B.C. and A.D. in others. Each pack says which on its own card, before you start.