Converting to local time using UTC time zone format in Javascript

Question

Been trying to wrap my head around this for a good time now, but I can't think of a good way to do it.

I have an array with a bunch of different UTC time zones (in just format -07, -01, +03, +10, etc). What I'm trying to achieve is a way to show the local time of those time zones, possibly including the day and month.

Here's an example of the resulting string: Local time: 14:09 23/08

• Eloi: You can read about how to mange date and time in JS here: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
• user15388024: You can use Date.prototype.getTimezoneOffset() to get your local timezone. Calculate the difference between your local timezone and the destination timezone, multiply it with 3600000 and add it to a Date object containing the current time.

Answer 1

You can use Date.prototype.getTimezoneOffset() to get your local timezone. Calculate the difference between your local timezone and the destination timezone, multiply it with 3600000 and add it to a Date object containing the current time.

const now = new Date();
const timezoneOffset = now.getTimezoneOffset() / 60;
const timezones = ['-07', '-01', '+03', '+10'];
timezones.forEach(timezone => {
 const difference = +timezone + timezoneOffset;
 const time = new Date(now.getTime() + difference * 3600000);
 console.log(`Local time: ${time.toLocaleTimeString([], { timeStyle: 'short', hour12: false })} ${time.toLocaleDateString([], { month: '2-digit', day: '2-digit' })}`);
});

• Piipperi800: How can I change this to a European format? Currently displays the time in 12 hr mm/dd which is the opposite of what I specified in the post. Edit: also, the code gives me the incorrect time by 3 hours, possibly because I'm on UTC+03 myself and the code thinks I'm on UTC+00?
• Piipperi800: Update: I managed to change the formatting, but I'm still not sure how to fix the time being incorrect...
• user15388024: @Piipperi800 I fixed it. getTimezoneOffset() returns the negative of what I expected.