getWeeksInYear

Signature

getWeeksInYear(value: string): number

import { getWeeksInYear } from "@northguild/gmt/plain/calculate";

Return the number of ISO weeks (52 or 53) in the ISO week-numbering year

• containing value.
• Uses value’s ISO week-numbering year (Temporal.PlainDate.yearOfWeek), not its calendar year — late-December/early-January dates can belong to a different ISO week-year than their calendar year (e.g. 2021-01-01 is ISO week-year 2020’s week 53).
• December 28 always falls in the ISO week-numbering year’s final week (ISO week 1 always contains Jan 4, so Dec 28 — exactly 52 weeks after — is always in the last week), so its weekOfYear reports the year’s total week count.
• Returns null on invalid input.

Parameters

Parameter	Type	Description
value	string	ISO PlainDate string

Returns

52 or 53, or null on invalid input

Examples

getWeeksInYear("2024-06-15") // 52
getWeeksInYear("2020-06-15") // 53
getWeeksInYear("2021-01-01") // 53 (belongs to ISO week-year 2020)
getWeeksInYear("invalid") // null

Source

plain/calculate/getWeeksInYear.ts