What should I use to add scheduling features to my app?

It depends on what kind of “scheduling” you mean, but here are the usual best options:

If you mean user-friendly event/appointment scheduling

Use a calendar/scheduling UI library or a booking system API.

Good options:

• Google Calendar API — if you want events synced with Google Calendar
• Microsoft Graph Calendar API — for Outlook/Office 365 integration
• Calendly API — if you want appointment booking and availability handling
• FullCalendar — great for building a calendar UI in web apps
• React Big Calendar / DayPilot — if you’re using React or need richer scheduling views

If you mean recurring jobs/background tasks in your app

Use a job scheduler or cron-like service.

Good options:

• Cron / systemd timers — simple server-side scheduling
• Celery Beat — for Python apps
• BullMQ / Agenda — for Node.js
• Sidekiq Cron — for Ruby
• Quartz — for Java
• APScheduler — for Python

If you want reminders/notifications

Combine scheduling with:

• a job queue
• push notifications
• email/SMS services like Twilio, SendGrid, Firebase Cloud Messaging

Quick recommendation

• For a web app calendar: FullCalendar + backend API
• For booking appointments: Calendly API or your own availability logic
• For automated tasks: cron/Celery Beat/BullMQ, depending on your stack

If you tell me:

1. your tech stack,
2. whether you mean appointments or background jobs,
3. whether you need recurring scheduling,

I can recommend the best specific tool.