addBusinessDays

Signature

addBusinessDays(value: string, amount: number, calendar?: BusinessCalendar): string

Return a PlainDate ISO string with amount working days added to value.

calendar names the weekend days and holidays to skip. Omit it and GMT keeps its original fixed Monday–Friday week with no holidays. Pass one anywhere the weekend is not Saturday–Sunday — much of the Middle East is Friday–Saturday.
Negative amount walks backwards, so addBusinessDays(value, -3, cal) and subtractBusinessDays(value, 3, cal) agree.
amount of 0 returns value unchanged — including when value is not itself a working day. Use rollDate to move a non-working day onto one.
value is never counted, so adding 1 from a holiday lands on the next working day after it.
value and calendar.holidays are local dates; calendar.timeZone is not read. A caller holding an instant reduces it to a local date first, with floorToZone.
Returns "" on invalid input — including a fractional amount, which names no whole number of working days — on an invalid calendar, and when the walk runs past 200,000 calendar days (about 547 years) without finishing.

Parameter	Type	Description
`value`	`string`	ISO PlainDate string
`amount`	`number`	whole number of working days to add; negative walks backwards
`calendar`	`BusinessCalendar`	optional BusinessCalendar; defaults to Monday–Friday with no holidays

ISO PlainDate string after adding working days, or "" on invalid input

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

addBusinessDays("2024-03-15", 1) // "2024-03-18" (Friday to Monday)