How can I check if my HBook iCal calendars are cached?

🤔 Problem

I would like to know if my external platforms are getting a cached calendar instead of the updated calendar.

In HBook > ICal Sync, we add a notification when we detect that your HBook iCal URL are cached. This article is useful if you wish to double-check by yourself.

🌱 Solution

You can use this tool which is very handy to reproduce a server-to-server call to your HBook iCal calendar URL: https://icalendar.org/validator.html

1. Enter the URL of your HBook iCal calendar. You will find it in HBook > iCal sync, when clicking on “Get export URL” for one of your accommodation.

2. Click on “Validate”.

3. Click on “Show source”

4. Search for the iCal property “DTSTAMP” and take note of it. It will be with the following format:, which means 28th of March 2025 at 14h26min25s (UTC time)

   CODE

   DTSTAMP:20250328T142625Z

5. Open a new tab and repeat the steps 1 to 4, with the same calendar URL.

If the DTSTAMP are identical, it means that there is caching applied on your calendar. The calendar given to your external platforms is the one that dates back to the date/time of the DTSTAMP value.

The DTSTAMP property is a timestamp of when the calendar was generated. It is never the same, as the calendar should be generated “as new” each time it is called, to be able to reflect any new reservation.

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