---
title: Dates and time
description: Why every entry sits on the local day the person saw, and how OWLF flags guesses.
---

**An entry belongs to the calendar day the person saw in the app.** Producers never derive that day from a UTC timestamp: an entry written at 23:30 in Berlin stays on that day, even though it is the next day in UTC.

| Field | When |
| --- | --- |
| `date` + `time` | Always. Local day and wall-clock time; `time` is `null` when unknown. |
| `instant` | The file stores an absolute moment: epoch or offset. [RFC 3339](https://www.rfc-editor.org/rfc/rfc3339) with seconds and offset: `2026-03-01T21:40:00+01:00`. |
| `zoneless` | `instant` comes from a bare epoch, so `date` and `time` are a guess in the converting device's zone. Consumers re-derive the day in the person's zone. |
| `utcDate` | The file prints a UTC day next to a local time. Consumers re-derive the day in the person's zone. |

`instant` wins over `date` + `time` for ordering. A consumer that knows the person's time zone should use it to re-derive the day whenever `zoneless` or `utcDate` is set.