isSameYear

Checks if two dates are in the same year.

Accepts any DateLike input (Date, timestamp, or date string).

Available since v2.0.0

Import

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

Signature

isSameYear(date1: DateLike, date2: DateLike): boolean

Parameters

Parameter	Type	Description
date1	DateLike	First date
date2	DateLike	Second date

Returns

boolean — True if same year, false otherwise (including when either date is invalid)

Examples

isSameYear

isSameYear('2025-01-01', '2025-12-31') // => true
isSameYear('2024-12-31', '2025-01-01') // => false

Related Types

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