# Timezones

###### tags: `timezone`

## Timezone
- A time zone is a region on Earth that has a uniform, legally mandated standard time.
- Example: "America/Los_Angeles", "Asia/Saigon"
- Almost all time zones on land have legally defined borders which coincide with the borders of the country mandating the time or some subdivision thereof.

## Time Zone != Offset
- An offset is a number that represents how far a particular date/time value is ahead or behind UTC
- Most offsets are expressed in whole hours.
- But there are many that are 30-minute offset.
- And there are a few that are 45-minute offset.
- A time zone contains much more:
- A name or ID that can be used to identify the zone.
- One or more offsets from UTC
- The specific dates and times that the zone transitions between offsets.
- Sometimes, a separate language-specific display name that can be presented to a user.
- One can determine the correct offset, given a time zone and a datetime. But one cannot determine the correct time zone given just an offset.

- Refs
- [Stackoverflow Wiki](https://stackoverflow.com/tags/timezone/info)
- [How to initialize a JavaScript Date to a particular time zone](https://stackoverflow.com/questions/15141762/how-to-initialize-a-javascript-date-to-a-particular-time-zone/15171030#15171030)