"I knew for months before I said anything." Maybe. Or maybe the ending has quietly reached back and edited the beginning, and the months are a story the ending is telling, not a fact the beginning left behind.
Knowing the ending rewrites the beginning
Baruch Fischhoff's research on hindsight bias found that once people know how something turned out, they reliably misremember having found that outcome more predictable — or, depending on the framing, having noticed the warning signs earlier — than they actually did in real time.1 The date you "first noticed" is exactly the kind of detail hindsight is likely to have quietly adjusted.
The rewrite doesn't feel like a guess
Richard Nisbett and Timothy Wilson's research on introspection found that people confabulate fluent, confident accounts of their own past mental states with no felt sense of uncertainty — the account arrives feeling remembered, not invented, even when it's substantially the second one.2 This is exactly why a hindsight-shifted date doesn't register as suspicious when you report it. It feels like recall, not reconstruction.
Later information gets absorbed into the memory of the earlier moment
Elizabeth Loftus and John Palmer's classic work showed that information learned after an event measurably alters recall of the event itself.3 The exact week a problem first became visible to you is a strong candidate for this kind of retroactive editing, precisely because so much relevant information gets learned only after the fact — most of it long after the week in question actually happened.
If the date matters — and sometimes it genuinely does, for your own sense of what you missed or didn't — the only way to check it against anything other than your current story is a contemporaneous record, made before the ending existed to do any editing. Related: when something happened is part of what it meant and why "he's always been like that" is usually wrong.
- Fischhoff, B. (1975). Hindsight is not equal to foresight: The effect of outcome knowledge on judgment under uncertainty. Journal of Experimental Psychology: Human Perception and Performance, 1(3), 288–299.
- Nisbett, R. E., & Wilson, T. D. (1977). Telling more than we can know: Verbal reports on mental processes. Psychological Review, 84(3), 231–259.
- Loftus, E. F., & Palmer, J. C. (1974). Reconstruction of automobile destruction: An example of the interaction between language and memory. Journal of Verbal Learning and Verbal Behavior, 13(5), 585–589.