I have a 30 day cycle. As long as I am cycling (post puberty and 8 months after the birth of my daughter) I am regular as the seasons.
I have been "late", three times in my life.
When I was twenty (I am 26 now) and was not on birth control, I had my regular menses, and then continued to spot for a month and a half. It took another month before I synced back up. I went into the Doctor, and she ran tests, did a pap, etc. Nothing was amiss, she said.
The second time was when I was twenty-one and pregnant with my daughter.
The third (I have a paragaurd IUD) was this past winter, after my marriage. I took two pregnancy tests (my mom has gotten pregnant while she had an IUD) and was flipping out. Big time. On the full moon, I began bleeding (I had been synced with the new moon). Wild stuff our bodies do sometimes. Wild.