Eenuh; castling! If you haven't moved either the castle (rook) or the king, the squares between them are unoccupied then you can move the king two squares towards the rook and place the rook the other side of the king - ONLY if the two squares the king passes through are not being attacked by the opponent. You'd think it's the offside of the chess world, but actually there's the en passant (passent?) rule which is slightly harder to follow and not generally one that ever occurs!
Time isn't massively relevant! We can have time limits of like 2 hours maybe, or a day, or whatever.