Howdy Rafe,
Good question. The deprecated functions will be logged as E_NOTICES. However, WordPress might be setup to suppress the logging of those errors. Before you can see those error you will need to set WP_DEBUG to true. However as noted in that article you might not want these errors to be publicly visible on your site, unless it is a testing or staging site. So you might want to set “WP_DEBUG_LOG” to true and set “WP_DEBUG_DISPLAY” to false after enabling WP_DEBUG itself.
Once you have logging setup navigating around the calendar will start generating those errors. If you visit a page or do an action that involves a deprecated function, the function name and its replacement should be in your logs.
Does that sound like a plan?
Cheers!
– Brook