Originally posted by Mad Rook
I've never played in a tournament that offers different day schedules, but looking at the tournament ads, it seems fairly clear to me. Since not everyone can take 5 vacation days to play chess, some tournaments offer shorter schedules. So for any particular section, you initially have a different group of players for each day schedule. The people playing in viewpoint, but I guess sometimes the organizers have to deal with the problems of modern life.
Yes, typically in fairly big tournaments (such as a six-round swiss event or more) multiple schedules will be offered but will merge at some point, for example before the last 3 rounds.
A side effect of this is that some tournaments will give players the option of "re-entering" the tournament (at a slightly discounted entry fee) after a bad start. This often leads to overly optimistic chess players squandering more money, but I once used this practice to good effect. I got off to a bad start (1 out of 3) in a 7-round event, and then re-entered into the 2-day schedule. The way this works, again, is with different time controls: for the 2-day schedule, the first four rounds were game in 45 minutes, and afterwards the different schedules merged and all games were 40 moves in 2 hours, sudden death 1 hour. I scored 6 out of 7 and tied for first.