How events from multiple sites are found and displayed

When you choose to get events from multiple events lists on one site or multiple sites, you may find that not all events are shown, or that it may take longer for some events to show than others. This is because the Events web part relies on SharePoint search to find events.

A high-level overview of how search works

SharePoint search must first “crawl” lists (like an events list) on sites, and then add the information it finds to a search index. Once indexed, the search engine finds matching results to queries (like the query sent from the Events web part). Once the matching results are found, the Events web part can display them.

Most of the time this process is fast, but the amount of time it takes can depend on how search is set up in your organization, how many sites there are, and how much information search is indexing at one time. The time it takes can also vary according to computer and network configurations. To ensure that all events display, it is important to manually request crawling and re-indexing of the site.

How custom mapping of crawled properties can affect your results

As mentioned above, search discovers information by crawling items on your site. The discovered content and metadata are called properties of the item. A search schema has a list of crawled properties that helps the crawler decide what content and metadata to extract. Not all crawled content or metadata is useful to have in the search index, so the search schema has a list of useful types of content and metadata, called managed properties. The index only includes content and metadata from the managed properties. Examples of useful metadata for the index are the author and the title of a document. Learn more about the search schema and properties.

Crawled properties can be mapped to managed properties to appear in search results.  If you're not seeing the events you expect to see on your page, it may be because of a mapping issue. Your site collection search administrator can ensure that the following crawled properties are mapped to managed properties: 

In addition, the search admin must re-index the site. Learn how to re-index a site.