Dates & Time

Modern lightweight

• ★ date-fns — function-per-operation, tree-shakeable. Default for most TS projects.
• ★ Day.js — Moment-compatible API in 2KB. Drop-in if you have legacy Moment code.
• Luxon — IANA time zones first-class; powerful but heavier.

The future

• ★ Temporal API — TC39 stage 3 / shipping in modern engines (V8 behind a flag, available via polyfill @js-temporal/polyfill). Will eventually replace Date entirely; worth learning now.

Pickers / calendar UIs

• react-day-picker — used by shadcn/ui's Calendar component. The default React date picker.
• react-aria DateField / DatePicker — accessibility-first.
• react-datepicker — older, mature.
• MUI X Date Pickers — if you're on MUI.
• vaul + react-day-picker — mobile drawer + calendar.

Time zones

• @js-temporal/polyfill — full IANA support, stable API.
• date-fns-tz — adds time zone support to date-fns.
• Luxon — has it built in.

Date math / scheduling

• rrule.js — RFC 5545 recurrence rules; for "every 3rd Monday" calendaring.
• ical-generator / node-ical — create / parse iCalendar.
• chrono-node — natural language date parsing ("next Tuesday").

Avoid for new code

• Moment.js — in maintenance mode; use Day.js as a drop-in or migrate to date-fns/Luxon/Temporal.

Pick this if…

• Default new project: date-fns (or Temporal polyfill if you want to lean future).
• Time-zone-heavy app: Luxon or Temporal.
• Replacing Moment without a rewrite: Day.js.
• Date picker UI: react-day-picker (especially with shadcn).