Something is colder than it used to be, or warmer, and you can feel the difference clearly enough. What you usually can't do, from feeling alone, is name the week it started — and "a while back" is not the same fact as an actual date, even though it can feel like one.
A feeling tells you "different." It doesn't tell you "since when."
The felt sense of change is real and often accurate about direction. It is undated by default. Something else has to be holding the calendar for a felt shift to become a locatable moment rather than a vague, sliding impression that gets vaguer the longer you try to pin it down.
Placing a memory in time is a specific skill, not a side effect of noticing
Endel Tulving's concept of autonoetic consciousness — the capacity to place a memory in personal, subjective time — describes an achievement distinct from simply recalling that something happened.1 Without deliberately tagging entries by when, the content of what changed tends to survive in memory far better than the timing of the change does, which is exactly backward from what you need if the question is "since when."
Memory reorganizes around a turning point once it's actually located
Martin Conway and Christopher Pleydell-Pearce's account of autobiographical memory describes how, once a turning point is identified, memory reorganizes around it as a boundary between a "before" and an "after."2 The risk, absent a real record, is that this reorganization happens around an invented boundary — likely the most emotionally intense moment you can recall, per Donald Redelmeier and Daniel Kahneman's findings on peak-driven memory3 — rather than the actual week the temperature first shifted, which may have been quieter and earlier than the moment that comes to mind first.
Finding the real week usually means going back through dated entries and watching the tone change, rather than trusting the one dramatic memory that volunteers itself first. See also the relationship temperatures we don't notice ourselves changing and when something happened is part of what it meant.
- Tulving, E. (1985). Memory and consciousness. Canadian Psychology, 26(1), 1–12.
- Conway, M. A., & Pleydell-Pearce, C. W. (2000). The construction of autobiographical memories in the self-memory system. Psychological Review, 107(2), 261–288.
- Redelmeier, D. A., & Kahneman, D. (1996). Patients' memories of painful medical treatments: Real-time and retrospective evaluations of two minimally invasive procedures. Pain, 66(1), 3–8.