Okay, sorry about that. I think I see what doesn't sound right. The way I understand it, stress/illness etc. can affect when you ovulate. For example, if you normally ovulate on day 14 of your cycle, but you get sick around then, that could possibly postpone your ovulation. Same thing if you're traveling or under high stress or whatever. It's also possible that stress can make you ovulate earlier than you normally would too.
However, there is usually a very regular amount of time between when you ovulate and when you have your period. That is called your luteal phase (I think!) The average is about 14 days--that's 14 days from when you ovulate to when your period starts again. (That's just the average for many women though--it could be different for you--mine is 11 days actually. But it is generally the same each month for each woman. Does that make sense? So mine is usually 11 days long--it may once in a while be 10 or 12, but won't vary much more than that. But another woman may have a 16 day luteal phase--which may vary a bit, but not by more than a day or so.)
What I was saying is that being stressed out or ill when you are supposed to start your period won't delay your period (or make it come earlier). Once you have ovulated, the time you start your period is already set--no amount of illness or stress or vacationing will change it. (Well, except pregnancy, of course!!
I guess I'm just saying that if you're trying to look for factors for why your period started later or earlier than usual, you will want to look back to what was happening a few weeks ago--when you most likely ovulated.
Does that make any sense? I'm trying to explain what I read in TCYOF a while back, and it's the middle of the night again--forgive me!