Look what we found in the SF Gateway archives:
For almost two centuries the huge spaceship had speared its way through the stars, bound for another two hundred years of travel before it would put down on a new planet, a new home for the Earth people.
On board the metal-enclosed worldlet were four hundred people: the last survivors of Earth. It was up to them to start life anew, to correct the mistakes their ancestors made.
But as the tenth generation neared maturity, the idle passengers found themselves face to face with these same problems – and this time there was no place to run and hide or to postpone their answers. For their miniature society was changing faster and faster. An the spaceship suddenly seemed destined to end as a star-bound coffin.
200 Years to Christmas? Nope. Just the one . . .