# Convert a time between time zones

Industry: Core

There is one function for each starting point. All three return a zoned string: the local date and time, the offset, and the zone name in brackets (RFC 9557).

## From a zoned value

```js
import { convertZonedToZoned } from "@northguild/gmt/zoned/convert";

convertZonedToZoned(
  "2024-07-15T12:00:00+02:00[Europe/Berlin]",
  "America/St_Johns",
); // "2024-07-15T07:30:00-02:30[America/St_Johns]"
```

`America/St_Johns` is 3 hours 30 minutes behind UTC in standard time and 2 hours 30 minutes behind in summer. The offset keeps its minutes, and one sign covers hours and minutes (RFC 3339 §5.6, `time-numoffset`).

## From a UTC instant

```js
import { convertUtcToZoned } from "@northguild/gmt/utc/convert";

convertUtcToZoned("2024-07-15T10:00:00Z", "Asia/Tokyo"); // "2024-07-15T19:00:00+09:00[Asia/Tokyo]"
```

## From a wall-clock time

A wall-clock time has no zone yet, so you name the zone it belongs to.

```js
import { convertPlainDateTimeToZoned } from "@northguild/gmt/zoned/convert";

convertPlainDateTimeToZoned("2024-07-15T12:00:00", "Asia/Kolkata"); // "2024-07-15T12:00:00.000+05:30[Asia/Kolkata]"
```

If the wall-clock time falls in a gap or an overlap on the day the clocks change, pass a `disambiguation`. [Check whether a local time exists on a DST day](../check-local-time-exists/) shows how.

## What to expect

| Starting point | Function | Result |
| --- | --- | --- |
| Zoned value | `convertZonedToZoned(value, timeZone)` | `"2024-07-15T07:30:00-02:30[America/St_Johns]"` |
| UTC instant | `convertUtcToZoned(value, timeZone)` | `"2024-07-15T19:00:00+09:00[Asia/Tokyo]"` |
| Wall-clock time | `convertPlainDateTimeToZoned(value, timeZone)` | `"2024-07-15T12:00:00.000+05:30[Asia/Kolkata]"` |

Invalid input, such as an unknown zone name, returns `""`.

In Temporal the same three steps are `withTimeZone`, `Instant.toZonedDateTimeISO` and `PlainDateTime.toZonedDateTime`. [Native Temporal and GMT](/gmt/migrate/temporal/) lists them.

Checked on 2026-10-26 with GMT 1.20.0.

See also: [`convertZonedToZoned`](/gmt/reference/zoned/convert/convertZonedToZoned/), [`convertUtcToZoned`](/gmt/reference/utc/convert/convertUtcToZoned/), [`convertPlainDateTimeToZoned`](/gmt/reference/zoned/convert/convertPlainDateTimeToZoned/).