timezone - Getting the client's time zone (and offset) in JavaScript

Question

How can I gather the visitor's time zone information?

I need both:

1. the time zone (for example, Europe/London)
2. and the offset from UTC or GMT (for example, UTC+01)

Answer 1

Using an offset to calculate Timezone is a wrong approach, and you will always encounter problems. Time zones and daylight saving rules may change on several occasions during a year, and It's difficult to keep up with changes.

To get the system's IANA timezone in JavaScript, you should use

console.log(Intl.DateTimeFormat().resolvedOptions().timeZone)