getTimezoneOffset

Returns the UTC offset in minutes for the given IANA timezone at a specific point in time.

A positive value means the timezone is ahead of UTC (e.g. +60 for CET). Returns null if the timezone is invalid or the date cannot be parsed.

The implementation uses Intl.DateTimeFormat to extract the local representation in the target timezone, then computes the delta from UTC.

Available since v2.0.0

Import

import { getTimezoneOffset } from '@helpers4/date';

Signature

getTimezoneOffset(tz: string, date: DateLike): number | null

Parameters

Parameter	Type	Description
tz	string	IANA timezone identifier (e.g. 'America/New_York')
date	DateLike	Reference date (defaults to now)

Returns

number | null — Offset in minutes, or null if inputs are invalid

Examples

getTimezoneOffset

getTimezoneOffset('America/New_York', '2025-01-19T12:00:00Z') // => -300 (EST)
getTimezoneOffset('Europe/Paris', '2025-07-19T12:00:00Z')     // => 120  (CEST)

Related Types

FormatInTimezoneOptions

Options for formatInTimezone.

interface FormatInTimezoneOptions {
  formatOptions?: DateTimeFormatOptions;
  locale?: string;
}

DateLike

A value that can be converted to a Date.

• Date — used as-is (validated for Invalid Date)
• number — treated as a timestamp (seconds or milliseconds, auto-detected); 0 is treated as invalid and produces null in ensureDate
• string — parsed via new Date(string)
• EpochMilliseconds — any object with a epochMilliseconds property (e.g. Temporal.Instant, Temporal.ZonedDateTime)

// TODO: When the Temporal API reaches Stage 4 and is available without // flags in all major runtimes, consider narrowing the union to the // concrete Temporal types for stricter type-checking.

type DateLike = Date | number | string | EpochMilliseconds

EpochMilliseconds

An object that exposes an epoch timestamp in milliseconds.

This structural type is satisfied by Temporal.Instant and Temporal.ZonedDateTime (and any future object that carries the same property), so callers can pass Temporal values without importing them.

interface EpochMilliseconds {
  epochMilliseconds: number;
}

Source

View source on GitHub