A property owner may have listed their property with 3 different web sites to gain a fair amount of exposure across the Internet.

A potential customer decides to book a two week holiday in August.

This means the property owner has to log into each of the 3 accounts to update each availability calendar.
This is where complications can arise. Forgetting to update just one calendar out of the 3 could cause possible problems with 'double bookings' or potentially losing a customer.

CIPS... One Calendar...Multiple Sites!