rrule
JavaScript library for working with recurrence rules for calendar dates.
itty-time
Ultra-small (~390 bytes) library for TTL date math and converting ms durations to and from strings.
@breejs/later
Maintained fork of later. Determine later (or previous) occurrences of recurring schedules
gl-w-date-frontend
Common code for using among web front-end development such as ES6+ and TypeScript