If you manage a rental property on Airbnb, Booking.com, Vrbo, or any other short-term rental platform, you've almost certainly bumped into the term iCal sync. Every major platform exposes your calendar as an iCal feed and lets you import feeds from other platforms. Understanding how this works — and where it falls short — is essential for any host managing listings in more than one place.

Why Booking Platforms Use iCal

Short-term rental platforms need to show guests which dates are available before they can book. When a host lists the same property on multiple platforms, each platform needs to know about bookings made on all the others — otherwise two guests might book the same dates at the same time. This is called a double booking, and it's the nightmare every multi-platform host wants to avoid.

Rather than build direct integrations with every competitor, platforms settled on a common denominator: the iCalendar format (RFC 5545). It's an open standard, plain-text, and already supported by every calendar application on the planet. Each platform publishes a URL that returns an ICS file representing the property's blocked/booked dates. Any other system can fetch that URL and import the blocks into its own calendar.

What an Airbnb iCal Feed Looks Like

When you export your Airbnb calendar, you get a URL that returns a live ICS file. Each booked or blocked date range appears as a VEVENT component. A simplified example:

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Airbnb Inc//Hosting Calendar 1.0//EN
X-WR-CALNAME:Airbnb (Beach House)

BEGIN:VEVENT
DTSTART;VALUE=DATE:20260601
DTEND;VALUE=DATE:20260605
SUMMARY:Airbnb (Not available)
UID:abc123xyz@airbnb.com
END:VEVENT

BEGIN:VEVENT
DTSTART;VALUE=DATE:20260610
DTEND;VALUE=DATE:20260612
SUMMARY:Reserved
UID:def456uvw@airbnb.com
END:VEVENT

END:VCALENDAR

A few things to note about how platforms use this format:

All-day events: Rental availability is expressed as all-day date ranges using DTSTART;VALUE=DATE rather than timestamps with times. The DTEND date is exclusive — a booking ending on June 5 means the guest checks out on June 5, not that June 5 is blocked.
Minimal metadata: The SUMMARY is typically vague ("Not available", "Reserved", or the platform name). Platforms deliberately withhold guest names and booking details for privacy.
Unique IDs: Every event carries a UID that the importing platform uses to identify whether an event is new, updated, or deleted on re-sync.

How Booking.com Does It

Booking.com follows the same iCal standard but has a few quirks worth knowing:

Booking.com exports use SUMMARY:Booking.com for all events — there's no distinction between confirmed bookings and manually blocked dates in the feed itself.
Their iCal export URL is found under Property > Calendar > Sync calendars > Export calendar.
Booking.com also supports importing external iCal feeds, which it polls on its own schedule (typically every few hours).

The Polling Problem

Here's the critical limitation: iCal sync is not real-time. There is no push mechanism. Each platform independently polls the imported feed URLs on its own schedule — typically every 15 minutes to a few hours, depending on the platform and your subscription tier.

This means there's always a window of time during which a booking on Platform A hasn't yet been reflected on Platform B. For a high-demand property with back-to-back bookings, that window is enough to allow a double booking. The iCal approach is a practical compromise, not a perfect solution — which is why serious multi-platform operators often use a channel manager (software that has direct API integrations with platforms) instead of relying solely on iCal sync.

What Each Platform Supports

Platform	Export iCal	Import iCal	Typical sync frequency
Airbnb	Yes	Yes	~1 hour
Booking.com	Yes	Yes	~2–4 hours
Vrbo / HomeAway	Yes	Yes	~1–2 hours
TripAdvisor / FlipKey	Yes	Yes	~4 hours
Google Calendar	Yes	Yes	~12–24 hours

Key Takeaways

iCal sync is pull-based: the importing platform fetches the feed on its own schedule.
Feeds carry blocked date ranges only — no guest details, pricing, or booking metadata.
The exclusive DTEND convention means you need to read date ranges carefully when building tools on top of these feeds.
For high-volume or luxury properties, consider a channel manager with real-time API connections for zero double-booking risk.