Coming from date-fns

The business-day functions in date-fns only know Monday to Friday. The translations below are checked against the real date-fns in test/date-fns.test.ts.

import { addBusinessDays, differenceInBusinessDays, format } from 'date-fns';
import { addWorkdays, workdaysBetween } from 'temporal-workdays';

format(addBusinessDays(new Date(2026, 10, 6), 3), 'yyyy-MM-dd'); // → '2026-11-11'
addWorkdays(Temporal.PlainDate.from('2026-11-06'), 3).toString(); // → '2026-11-11'

differenceInBusinessDays(new Date(2026, 10, 16), new Date(2026, 10, 9)); // → 5
workdaysBetween(Temporal.PlainDate.from('2026-11-09'), Temporal.PlainDate.from('2026-11-16')); // → 5

date-fns	temporal-workdays
addBusinessDays(date, n)	addWorkdays(d, n), which always gives the same result
isWeekend(date)	isWeekend(d)
differenceInBusinessDays(later, earlier)	workdaysBetween(earlier, later) when both are workdays, otherwise see below

Going forward, differenceInBusinessDays counts from the earlier date up to, but not including, the later one. When either date can be a weekend day and you need its exact result, move both dates back one day:

import { differenceInBusinessDays } from 'date-fns';
import { workdaysBetween } from 'temporal-workdays';

const saturday = Temporal.PlainDate.from('2026-11-07');
const monday = Temporal.PlainDate.from('2026-11-09');

differenceInBusinessDays(new Date(2026, 10, 9), new Date(2026, 10, 7)); // → 0
workdaysBetween(saturday.subtract({ days: 1 }), monday.subtract({ days: 1 })); // → 0

Going backward, with later before earlier, workdaysBetween(earlier, later) already gives its exact result.