Pages listed here have an {{event}} template with a date which has already gone by. The date should be updated to the next event, or the listing should be removed if there are no future editions.
It is acceptable to have something out of date if the following years dates are not yet fixed.
This website uses the Wikivoyage API to get and display all the information you see. This is the MediaWiki API, which is a general API for accessing data from Wikimedia projects. You can find information about it here: MediaWiki API.