> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vitasync.io/llms.txt
> Use this file to discover all available pages before exploring further.

# A day of data

> One record per calendar day, with only the metrics you logged.

Everything you log hangs off one record per calendar day. A day holds only the metrics you logged. A person tracking sleep and spending has days with two values on them.

```mermaid theme={null}
flowchart TB
  day["Wednesday 14 October"]
  day --> sleep["Sleep: 7.4 h, quality 8"]
  day --> mood["Mood: 6, 8 and 7 (average 7)"]
  day --> steps["Steps: 8,412 from Health Connect"]
  day --> food["Food: 3 meals, 1,980 kcal"]
  day --> work["Deep Work: two sessions, 3.5 h"]
  day --> habits["Habits: 3 of 4 ticked"]
  day --> custom["Headache: no"]
```

## Blank is not zero

A metric you did not log is blank. VitaSync never writes a zero for you. Insights only use days with a value, so a skipped day does not drag an average down.

One exception: a soreness check-in of 0 means you checked and were not sore. That zero is kept.

## Some metrics are made of smaller pieces

| Metric | Made of | The day's value |
| - | - | - |
| Mood, energy, stress | Check-ins through the day, each with a time | The average of the check-ins |
| Deep Work, meditation | Timed sessions | The sessions added up |
| Food | Food items, each with a meal and a serving | Calories and macros added up |
| Workouts | Sessions, each with its sets | Listed, not added |
| Water | Taps and presets | Added up, in ml |

## Your reference data

Some things are not about one day. They describe you, and the days refer to them.

```mermaid theme={null}
erDiagram
  DAY ||--o{ FOOD_ITEM : lists
  DAY ||--o{ WORKOUT : lists
  DAY ||--o{ CHECK_IN : "has (mood, energy, stress)"
  HABIT ||--o{ DAY : "is ticked on"
  SUPPLEMENT ||--o{ DAY : "is ticked on"
  CUSTOM_METRIC ||--o{ DAY : "has a value on"
  WORKOUT_TEMPLATE ||--o{ WORKOUT : starts
  GOAL }o--|| METRIC : targets
  REMINDER }o--o| METRIC : "nudges you to log"
```

Habits, supplements, custom metrics, workout templates, goals and reminders are kept once, not per day. Deleting a habit does not delete the days you ticked it on.

## Where a value came from

Every value carries a tag: typed by you, or read from a source like Health Connect. A value with no tag is yours. See [Where a value comes from](/how-it-works/sources).

## Clearing a value

Clearing a value does not just blank it. The phone records that you cleared it, so another phone with the same account learns about the clear. Otherwise the second phone could not tell "cleared" from "never logged".


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