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Would be great to be able to limit the number of calendars to the current year.
What you're asking can be done at the theme layer.
If you want to use your own calendar logic have a look at hotel_booking_preprocess_node to see how to add in the calendars before the node is shown. You can implement this in your theme (copy the function and rename the function to suit your theme name). There is a check box in the admin settings to turn off displaying calendars with the node, this allows you to intervene.
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