# An organization's time zone — the local time of every app that names none

> Each organization on Osyrin Cloud has one Time zone setting, on its settings page. An app whose source declares no `app.DefaultTimeZone` uses it as its local time — `DateTime.Now`, `DateTime.Today`, `ToLocalTime()` and `TimeZoneInfo.Local` read in it — from the app's next build. A zone the source declares always wins. The same setting is the midnight the organization's daily budgets reset at, so an owner can change it once every 30 days.

<!-- id: zones-organization-time-zone · area: zones · stability: stable · html: https://osysharp.com/reference/zones/organization-time-zone/ -->

## Summary        {#summary}

An app that never says which time zone it lives in still has a local time on Osyrin Cloud: its **organization's**. The
organization's **Time zone**, on its settings page, is the zone `DateTime.Now` and `DateTime.Today` read in for every
app of the organization whose source declares no `app.DefaultTimeZone`. An app that declares one keeps its own.

## Signature      {#signature}

```text
Organization settings → Time zone                        the organization's one zone (UTC until someone changes it)
app.DefaultTimeZone        (not written)                 local time is the organization's zone, on Osyrin Cloud
app.DefaultTimeZone = TimeZoneInfo.FindSystemTimeZoneById("Europe/Stockholm");   local time is Stockholm, always
app.DefaultTimeZone = TimeZoneInfo.Utc;                  local time is UTC, always
```

## Description    {#description}

### Which zone is local time in?   {#which-zone}

The first of these that applies:

| | local time is |
|---|---|
| the signed-in person set their own zone (a `[PreferredTimeZone]` member of the principal) | **their** zone |
| the app's source declares `app.DefaultTimeZone` | **that** zone |
| the app is deployed on Osyrin Cloud | **the organization's** Time zone |
| anywhere else — `osy launch`, `osy compile`, `osy test` on your own machine | **UTC** |

"Local time" is everything that reads the local clock: `DateTime.Now`, `DateTime.Today`, `DateTimeOffset.Now`,
`d.ToLocalTime()`, `d.IsDaylightSavingTime()`, `DateTime.Parse` of text that carries an offset, and
`TimeZoneInfo.Local` itself — on the server, in the browser and inside a query alike ([Time zones — TimeZoneInfo](https://osysharp.com/reference/stdlib/zones/),
[Current time (DateTime.UtcNow, DurableClock.Now)](https://osysharp.com/reference/function/current-time/)). A stored `DateTime` is unaffected: it is a UTC instant whichever zone reads it.

The organization's zone does not have to be one the app lists in its `zones { }` block. The organization chose it, not
the app's author, so the app is built with it whatever that block says.

### When does a change reach an app?   {#next-build}

**On the app's next build.** Local time is fixed when an app is built, so the server, the browser and the database all
agree on it without asking on each request. An app picks up a new organization zone the next time it is deployed, or
the next time Osyrin Cloud rebuilds it for a new platform release. Until then it keeps the zone it was built with. Run
`osy deploy` to move it at once ([Deploying your app to an environment](https://osysharp.com/reference/local/deploying-your-app/)).

### Keeping an app on its own clock   {#pin-the-app}

Declare the zone in the source and the organization's setting never touches that app. An app that must stay on UTC —
a log, a ledger reconciled against a bank's UTC statement — says so explicitly:

```osy title="this app stays on UTC whatever its organization's zone is" test app=zones-organization-time-zone-pinned
app.DefaultTimeZone = TimeZoneInfo.Utc;

entity Transfer {
  [Required, MaxLength(40)] string Reference;
  DateTime BookedAt;
}

/// The day a transfer is booked on — the UTC day, in every organization.
DateOnly BookingDay(Transfer t) => DateOnly.FromDateTime(t.BookedAt);
```

An app that leaves the line out follows its organization. Here "today" is the organization's today:

```osy title="no zone in the source: today is the organization's today" test app=zones-organization-time-zone
entity Shift {
  [Required, MaxLength(80)] string Who;
  DateOnly Day;
}

/// The shifts on today's rota, where "today" starts at midnight in the organization's zone.
List<Shift> TodaysShifts() {
  var today = DateOnly.FromDateTime(DateTime.Today);
  return Shift.Where(s => s.Day == today).OrderBy(s => s.Who).ToList();
}
```

### Changing it   {#changing-it}

Open the organization's **Settings** page in Osyrin Cloud; the **Time zone** section shows the current zone. Choose
**Change time zone**, pick the new one and **Save time zone**.

- **Who may change it:** an Owner of the organization. Everyone else sees the zone and a disabled button that says
  so.
- **Once every 30 days.** The same setting is the midnight the organization's daily budgets reset at — a billing
  boundary — so moving it again within 30 days is refused, naming the date it can change from. Saving the zone it
  already has is not a change and does not start the 30 days.
- **A new organization** starts in the time zone Osyrin Cloud sets for the region it was created in, or UTC where there
  is none. Choosing a zone for the first time is not limited.

The daily budgets on the organization's **Budgets** page reset at midnight in this zone ([What your plan allows, and how much of it is used](https://osysharp.com/reference/zones/plans-and-limits/)).

## See also       {#see-also}

[Time zones — TimeZoneInfo](https://osysharp.com/reference/stdlib/zones/) — `TimeZoneInfo`, `app.DefaultTimeZone` and a viewer's own zone.

[Current time (DateTime.UtcNow, DurableClock.Now)](https://osysharp.com/reference/function/current-time/) — `DateTime.Now`, `DateTime.Today` and the local clock.

[What your plan allows, and how much of it is used](https://osysharp.com/reference/zones/plans-and-limits/) — the plan and the budgets that reset at the organization's midnight.

[Deploying an application to a cloud platform — the zone builds it](https://osysharp.com/reference/zones/deploying-an-application/) — what a deploy does, including building the app.