Vielzeug

Date Ranges and Recurrence ​

Problem ​

Calendar views and schedules need lazy zoned sequences that advance safely across DST changes.

Solution ​

Use dateRange() for bounded ranges and recurrence() for count- or date-limited schedules.

ts
import { dateRange, parse, recurrence } from '@vielzeug/tempo';

const start = parse('2026-03-01T09:00:00[America/New_York]', { as: 'zonedDateTime' });
const end = parse('2026-03-03T09:00:00[America/New_York]', { as: 'zonedDateTime' });

const days = [...dateRange(start, end, { days: 1 })];
const fortnightly = [...recurrence(start, { count: 4, frequency: 'weekly', interval: 2 })];

Pitfalls ​

  • dateRange() rejects steps that do not advance time.
  • recurrence() requires a positive safe-integer interval and a non-negative safe-integer count.
  • Pass timeZone when the starting value is plain or an instant.