Hi Kuanyin,
If you get this book called Dark Shadows Memories (I think that is the title of it), it gives you the taping date and the broadcast date for each show. The shows were frequently taped out of order, though in some cases the numbering was consecutive for a period. So this is one reason why the actors today don't have a clue about the storylines unless they have taken the time to watch the old tapes. In some cases, the taping schedule had to be adjusted because some of the actors, such as Thayer David, had other commitments. Some of them were doing plays at the same time as the show was running ... Don Briscoe did Boys in the Band, Virginia Vestoff did 1776, and David Selby and Lara Parker both did plays that didn't run very long in 1969 or 1970.
When the schedule for taping the episodes was adjusted, the actors called it "re-ranking the shows."
Given this situation, it's amazing that ANYBODY had any degree of continuity at all on DS! but this is why in some instances they re-do a scene from the previous day's show with completely different costumes, or sets!
Best,
Gothick