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@northguild/gmt

subtractBusinessDays

Signature

Section titled “Signature”
subtractBusinessDays(value: string, amount: number, calendar?: BusinessCalendar): string

Return a PlainDate ISO string with amount working days subtracted from 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 behaves identically to addBusinessDays(value, Math.abs(amount), cal).
  • 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 subtracting 1 from a holiday lands on the working day before 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.

Parameters

Section titled “Parameters”
ParameterTypeDescription
valuestringISO PlainDate string
amountnumberwhole number of working days to subtract; negative walks forwards
calendarBusinessCalendaroptional BusinessCalendar; defaults to Monday–Friday with no holidays

Returns

Section titled “Returns”

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

Section titled “Related types”

Examples

Section titled “Examples”
import { subtractBusinessDays } from "@northguild/gmt/plain/calculate";


subtractBusinessDays("2024-03-18", 1) // "2024-03-15" (Monday back to Friday)
output 

Source

Section titled “Source”

plain/calculate/subtractBusinessDays.ts