mirror of https://github.com/therootcompany/tz.js
225 lines
5.3 KiB
Markdown
225 lines
5.3 KiB
Markdown
# [xtz.js](https://github.com/therootcompany/tz.js)
|
|
|
|
A fast, lightweight, zero-dependency library to translate between Time Zones and UTC with native `Intl.DateTimeFormat`
|
|
in ~100 LoC. For Node.js & Browsers.
|
|
|
|
[](https://therootcompany.github.io/tz.js/)
|
|
|
|
XTZ is a poor man's Temporal polyfill, but just for time zones. \
|
|
Demo: <https://therootcompany.github.io/tz.js/>
|
|
|
|
> What UTC time will it be when it's 3:15am in New York?
|
|
|
|
```js
|
|
// Relative New York time to Absolute UTC Time
|
|
TZ.toUTCISOString("2021-11-07 03:15:59.000", "America/New_York");
|
|
// "2021-11-07T03:15:59.000-0500"
|
|
```
|
|
|
|
```js
|
|
var tzDate = TZ.toUTC("2021-11-07 03:15:59.000", "America/New_York");
|
|
// {
|
|
// year: 2021, month: 11, day: 7,
|
|
// hour: 3, minute: 15, second: 59, millisecond: 0,
|
|
// offset: -300, timeZoneName: "Eastern Standard Time"
|
|
// }
|
|
|
|
tzDate.toISOString();
|
|
// "2021-11-07T03:15:59.000-0500"
|
|
// (same as "2021-11-07T08:15:59.000Z")
|
|
```
|
|
|
|
> What time will it be in New York when it's 7:15am UTC?
|
|
|
|
```js
|
|
// Absolute UTC time to Relative New York time
|
|
TZ.toTimeZoneISOString("2021-03-14T07:15:59.000Z", "America/New_York");
|
|
// "2021-03-14T03:15:59.000-0400"
|
|
```
|
|
|
|
```js
|
|
var utcDate = TZ.toTimeZone("2021-03-14T07:15:59.000Z", "America/New_York");
|
|
// {
|
|
// year: 2021, month: 3, day: 14,
|
|
// hour: 3, minute: 15, second: 59, millisecond: 0,
|
|
// offset: -240, timeZoneName: "Eastern Daylight Time"
|
|
// }
|
|
|
|
utcDate.toISOString();
|
|
// "2021-03-14T03:15:59.000-0400"
|
|
// (same as "2021-11-07T07:15:59.000Z")
|
|
```
|
|
|
|
# Features
|
|
|
|
- [x] Translate a UTC time to a Time Zone
|
|
- [x] Translate a Zoned time to UTC
|
|
- [x] Handles **Daylight Savings**, Weird Time Zones, etc...
|
|
- [x] Well-tested `npm run test`
|
|
- [x] Lightweight (No deps)
|
|
- 5kb Source + Comments
|
|
- 2.5kb Minified
|
|
- <1kb `gzip`d
|
|
|
|
Compatible with Browsers, and Node.js.
|
|
|
|
## Browsers
|
|
|
|
```html
|
|
<script src="https://unpkg.com/xtz@latest/xtz.min.js"></script>
|
|
```
|
|
|
|
```js
|
|
var TZ = window.XTZ;
|
|
```
|
|
|
|
## Node.js & Webpack
|
|
|
|
```bash
|
|
npm install --save xtz
|
|
```
|
|
|
|
```js
|
|
var TZ = require("xtz");
|
|
```
|
|
|
|
## Demo
|
|
|
|
See <https://therootcompany.github.io/tz.js/>.
|
|
|
|
# API
|
|
|
|
- `toTimeZone(utcDate, timeZone)`
|
|
- `toTimeZoneISOString(isoString, timeZone)`
|
|
- `toUTC(dtString, timeZone)`
|
|
- `toUTCISOString(dtString, timeZone)`
|
|
|
|
## `toTimeZone(utcDate, timeZone)`
|
|
|
|
> Convert UTC into a Target Time Zone
|
|
|
|
Use ISO timestamps representing the absolute UTC time in the target time zone:
|
|
|
|
```txt
|
|
"2021-11-07T08:15:59.000Z"
|
|
```
|
|
|
|
Convert directly to an ISO String:
|
|
|
|
```js
|
|
TZ.toTimeZoneISOString("2021-11-07T08:15:59.000Z", "America/New_York");
|
|
// "2021-11-07T03:15:59.000-0500"
|
|
```
|
|
|
|
Or use our bespoke (custom) date object:
|
|
|
|
```js
|
|
var tzDate = TZ.toTimeZone("2021-11-07T08:15:59.000Z", "America/New_York");
|
|
```
|
|
|
|
You can also use a date object with an absolute UTC time:
|
|
|
|
```js
|
|
var tzDate = TZ.toTimeZone(
|
|
new Date("2021-11-07T08:15:59.000Z"),
|
|
"America/New_York"
|
|
);
|
|
```
|
|
|
|
```js
|
|
console.log(tzDate.toISOString());
|
|
// "2021-11-07T03:15:59.000-0500"
|
|
```
|
|
|
|
Our ISO Strings + Offsets work with JavaScript's native Date object!!
|
|
|
|
```js
|
|
new Date("2021-11-07T03:15:59.000-0500").toISOString());
|
|
// "2021-11-07T08:15:59.000Z"
|
|
```
|
|
|
|
## `toUTC(dtString, timeZone)`
|
|
|
|
> Convert a Target Time Zone into UTC
|
|
|
|
Use ISO-like timestamps representing the _local_ time in the target time zone:
|
|
|
|
```txt
|
|
"2021-11-0 T03:15:59.000"
|
|
```
|
|
|
|
Convert directly to an offset ISO String:
|
|
|
|
```js
|
|
TZ.toUTCISOString("2021-11-07 03:15:59.000", "America/New_York");
|
|
// "2021-11-07T03:15:59.000-0500"
|
|
```
|
|
|
|
Or our bespoke date object:
|
|
|
|
```js
|
|
var utcDate = TZ.toUTC("2021-11-07 03:15:59.000", "America/New_York");
|
|
```
|
|
|
|
You can also use a date object as the source time, but the date's UTC time will be treated as **_relative to time
|
|
zone_** rather than absolute (this is a workaround for JavaScript's lack of bi-directional timezone support).
|
|
|
|
```js
|
|
var utcDate = TZ.toUTC(
|
|
new Date("2021-11-07T03:15:59.000Z"),
|
|
"America/New_York"
|
|
);
|
|
```
|
|
|
|
```js
|
|
utcDate.toISOString();
|
|
// "2021-11-07T03:15:59.000-0500"
|
|
```
|
|
|
|
# Daylight Savings / Edge Cases
|
|
|
|
> In 2021 Daylight Savings (in the US)
|
|
>
|
|
> - begins at 2am on March 14th
|
|
> - ends at 2am on November 7th
|
|
>
|
|
> See <https://www.timeanddate.com/time/change/usa>.
|
|
|
|
Q: What happens in March when 2am is skipped?
|
|
|
|
- A: Although 2am is not a valid time, rather than throwing an error this library will resolve to 1am instead, which
|
|
is an hour early in real ("tick-tock" or "monotonic") time.
|
|
```js
|
|
var utcDate = TZ.toUTC("2021-03-14 02:15:59.000", "America/New_York");
|
|
utcDate.toISOString();
|
|
// "2021-03-14T02:15:59.000-0400"
|
|
// (same as "2021-03-14T01:15:59.000-0500")
|
|
```
|
|
|
|
Q: What happens in November when 2am happens twice?
|
|
|
|
- A: Although both 2ams are distinguishable with ISO offset times, only the first can be resolved from a local time
|
|
with this library.
|
|
```js
|
|
var utcDate = TZ.toUTC("2021-11-07 01:15:59.000", "America/New_York");
|
|
utcDate.toISOString();
|
|
// "2021-11-07T01:15:59.000-0400", same as "2021-11-07T05:15:59.000Z"
|
|
// (an hour before the 2nd 2am at "2021-11-07T01:15:59.000-0500")
|
|
```
|
|
|
|
# List of Time Zones
|
|
|
|
See the [Full List of Time Zones](https://en.wikipedia.org/wiki/List_of_tz_database_time_zones) on Wikipedia.
|
|
|
|
Common Zones for Testing:
|
|
|
|
```txt
|
|
America/New_York -0500
|
|
America/Denver -0700
|
|
America/Phoenix -0700 (No DST)
|
|
America/Los_Angeles -0800
|
|
Australia/Adelaide +0930 (30-min, has DST)
|
|
Asia/Kathmandu +0545 (No DST, 45-min)
|
|
Asia/Kolkata +0530 (No DST, 30-min)
|
|
```
|