The St. Andrew Christmas Novena

Not nine days but twenty five, and the prayer is said fifteen times a day. An Advent discipline more than a novena, prayed from St. Andrew’s feast to Christmas Eve.

Length.
25 days.
Traditionally prayed.
30 November to 24 December
Sources.
Built from public-domain prayers plus original daily meditations written for this site.

If you miss a day, pick up where you left off. Nine consecutive days is the tradition and it is worth keeping when you can, but a broken chain does not undo what you have prayed, and starting again from day one is your choice rather than a penalty.

About the saint this novena asks