Turn your Outlook calendar into
a booking system
One OAuth click connects Microsoft 365 or Outlook.com. Real-time availability checks, automatic event creation, and Teams links on every booking.
Calendar conflicts cost you clients
is how 'what time works for you?' email threads end
Every back-and-forth message is another chance to lose the meeting. A booking link closes the loop in one step.
calendars is all it takes to start double-booking yourself
Work, personal, a shared team calendar: conflicts live in the gaps between them. Astrocal checks every connected calendar before showing a slot.
is what availability becomes when booking tools sync on a timer
Polling every few minutes leaves a window for conflicts. Astrocal reads your free/busy at the moment of each slot request. There is no cache to go stale.
How Microsoft 365 works with Astrocal
You: Create event types and connect Microsoft 365 via OAuth
One OAuth screen with PKCE, under 30 seconds
Astrocal: Reads FreeBusy data in real time
On every slot request, not cached
Client: Books via your link or widget
Picks from genuinely available slots
Outlook: New event created automatically
With invitee details and a Teams link in your Outlook calendar
Integration capabilities
| Capability | Supported | Notes |
|---|---|---|
| Real-time FreeBusy checks | Yes | Reads availability on every slot request via Microsoft Graph API |
| Write booking events to calendar | Yes | Created instantly on booking confirmed |
| Multiple Outlook calendars | Yes | Check multiple calendars for conflicts on all plans |
| Two-way sync | Partial | External events block availability in real time. Cancellations in Astrocal remove the Outlook event. Cancellations made directly in Outlook are not yet synced back. |
| Recurring events | No | On roadmap |
| Microsoft Teams links | Yes | Auto-added to bookings. Zoom and Google Meet supported too |
| Multiple hosts, round-robin | Yes | Each host connects their own Microsoft 365 calendar |
| Microsoft 365 work & school accounts | Yes | Personal Microsoft accounts and Microsoft 365 (work/school) accounts both supported |
| Meeting rooms / resources | No | On roadmap |
Available on all plans including Free.
One OAuth screen. That's the hard part.
Click 'Connect Microsoft 365'
You'll be taken to Microsoft's standard OAuth screen with PKCE. Astrocal requests calendar read/write access: the permissions needed to check availability and create booking events.
Create your first event type
Set a duration, your availability windows, and a buffer between meetings. Astrocal reads your calendar in real time from this point. No additional configuration needed.
Share your booking link or embed the widget
Anyone who books gets a confirmation email. An Outlook calendar event is created automatically with the invitee's details.
Pair Outlook with Google Calendar, Stripe, and more
Google Calendar
Use both Outlook and Google Calendar? Astrocal checks all connected calendars for conflicts.
Stripe
Require payment at the time of booking. The Outlook event is created only after payment clears.
Webhooks
Push booking data to any CRM, Slack, or automation tool via signed webhooks with automatic retries.
Frequently asked questions
Connect Outlook in 30 seconds
Real-time sync on every plan. Free to start, no credit card required.