getWeekNumber

Signature

getWeekNumber(dateStr: string, weekStartsOn?: "monday" | "sunday"): number

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

Calculate the week number based on configurable week start day.

• ISO (monday): Week 1 is the week containing the first Thursday (has at least 4 days in the year)
• US (sunday): Week 1 is the week containing Jan 1 (first week has at least 1 day)

Parameters

Parameter	Type	Description
dateStr	string	ISO PlainDate string (e.g. “2024-03-15”)
weekStartsOn	"monday" | "sunday"	optional: “monday” (default) or “sunday”

Returns

Week number (1-53), or null on invalid input

Examples

getWeekNumber("2024-01-01") // 1
getWeekNumber("2024-01-08") // 2
getWeekNumber("2024-12-31") // 1
getWeekNumber("2024-01-01", "sunday") // 1
getWeekNumber("invalid") // null

Source

plain/calculate/getWeekNumber.ts