Did this include your letters of rec? Princeton didn't send those out for everyone until the end of the month, so i wasn't complete until the first week of Sept.
The date on the snail mail was 8/26. I think it gave you a choice for either these three dates: 9/30, 10/2, & 10/7. My secondary application was sent 8/1 & my letters followed quickly. My AMCAS was only transmitted on like 8/8 or so. I think Dartmouth has quick turn around. I thought it was so quick that when I saw the letter for an interview in my mailbox, I thought it was a rejection letter.