The Explorer's Home in one read: Jump back in (the caller's Within reach set: the 4 documents they used on the most days over the last 90, then the 4 they used most recently, none twice; most used first) and What happened (other people's actions on documents the caller can open over the last 14 days, one group per document per day in `tz`). Query: `tz` (IANA, default UTC). 400 `tz_invalid`.