What should I use for calendar sync and availability management?

If you mean calendar sync + availability management for scheduling, the best choice depends on whether you need this for personal use, a team, or a product/app.

Good options

1. Google Calendar + Microsoft Outlook Calendar

Best if you just need reliable sync between calendars.

• Two-way sync support via native integrations or middleware
• Good availability sharing
• Widely supported by scheduling tools

2. Calendly

Best for availability management and booking.

• Connects to Google, Outlook, and Apple calendars
• Automatically shows open times based on your rules
• Prevents double-booking
• Great if people need to schedule meetings with you

3. Cron / Notion Calendar

Best for personal productivity and simple availability management.

• Clean UI
• Good for managing multiple calendars
• Less focused on external booking than Calendly

4. Microsoft Bookings

Best for organizations already using Microsoft 365.

• Availability-based scheduling
• Calendar integration with Outlook
• Good for service-based teams

5. Google Appointment Schedules

Best if you mainly use Google Calendar.

• Native booking pages
• Syncs directly with your calendar
• Simple to set up

6. Nylas / Cronofy

Best if you’re building a product and need calendar APIs.

• Sync calendar events across providers
• Availability lookup
• Booking and scheduling infrastructure
• More developer-oriented than end-user tools

Quick recommendation

• For personal scheduling: Google Calendar or Notion Calendar
• For booking meetings with others: Calendly
• For business team scheduling: Microsoft Bookings or Google Appointment Schedules
• For building your own app: Nylas or Cronofy

If you tell me:

1. whether this is personal, team, or app development, and
2. whether you use Google, Outlook, or Apple Calendar,

I can recommend the best exact option.