# Timezone

URL: https://caijiao.org/dayjs/plugin/timezone
Source: docs/dayjs/plugin/timezone.md
Description: Timezone 插件添加了 dayjs.tz .tz .tz.guess .tz.setDefault API，在时区之间解析或显示。

Timezone 插件添加了 dayjs.tz .tz .tz.guess .tz.setDefault API，在时区之间解析或显示。

```javascript
var utc = require("dayjs/plugin/utc");
var timezone = require("dayjs/plugin/timezone"); // dependent on utc plugin

dayjs.extend(utc);
dayjs.extend(timezone);

const timestamp = "2014-06-01 12:00";
const tz = "America/New_York";

const dayjsLocal = dayjs(timestamp); //assumes UTC
//dayjsLocal.toISOString() -> 2014-06-01T12:00:00.000Z
//dayjsLocal.format('YYYY-MM-DDTHH:mm:ss') -> 2014-06-01T12:00:00

const dayjsAmerica = dayjsLocal.tz(tz); //existing time treated as UTC
//dayjsAmerica.toISOString() -> 2014-06-01T12:00:00.000Z
//dayjsAmerica.format('YYYY-MM-DDTHH:mm:ss') -> 2014-06-01T08:00:00

const dayjsAmericaKeep = dayjsLocal.tz(tz, true); //existing time treated as local time
//dayjsAmericaKeep.toISOString() -> 2014-06-01T16:00:00.000Z
//dayjsAmericaKeep.format('YYYY-MM-DDTHH:mm:ss') -> 2014-06-01T12:00:00
```

推测用户时区

```javascript
dayjs.tz.guess();
```

解析时区的时间

```javascript
const d1 = dayjs.tz("2013-11-18 11:55", "Asia/Taipei");
d1.format(); // => 2013-11-18T11:55:00+08:00
d1.toISOString(); // => 2013-11-18T03:55:00.000Z
```

转换至目标时区

```javascript
const d2 = dayjs.utc("2013-11-18 11:55").tz("Asia/Taipei");
d2.format(); // => 2013-11-18T19:55:00+08:00
d2.toISOString(); // => 2013-11-18T11:55:00.000Z
```

设置/重置默认时区

```javascript
// Setting the default timezone
dayjs.tz.setDefault("America/New_York");

// Resetting the default timezone to the system timezone
dayjs.tz.setDefault();
```

## 和 Moment.js 的差异

Using the default timezone makes `moment(dateValue)` use this timezone (but `moment.tz(dateValue, timezone)` still requires the second parameter).

But `dayjs(dateValue)` always uses the local timezone, even if `dayjs.tz.setDefault` is used; only `dayjs.tz(dateValue)` (without second parameter) uses the default timezone.