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Date Ranges and Recurrence ​

Problem ​

Calendars and schedules need lazy sequences that preserve timezone and DST behavior.

Solution ​

Start with a zoned date-time, then use dateRange() or recurrence().

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

const start = parse('2026-03-01T00:00:00[Europe/Berlin]', { as: 'zonedDateTime' });
const end = parse('2026-03-31T00:00:00[Europe/Berlin]', { as: 'zonedDateTime' });

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

Pitfalls ​

  • dateRange() requires a forward-moving step.
  • Spreading a large generator materializes every result; prefer for...of for streams.
  • Plain inputs require an explicit timeZone option.